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  • 51. Nitze, Florian
    et al.
    Mazurkiewicz, Marta
    Malolepszy, Artur
    Mikolajczuk, Anna
    Kedzierzawski, Piotr
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hu, Guangzhi
    Kurzydlowski, Krzysztof Jan
    Stobinski, Leszek
    Borodzinski, Andrzej
    Wagberg, Thomas
    Synthesis of palladium nanoparticles decorated helical carbon nanofiber as highly active anodic catalyst for direct formic acid fuel cells2012In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 63, p. 323-328Article in journal (Refereed)
    Abstract [en]

    We present a single metal approach to produce highly active catalyst materials based on Pd-decorated helical carbon nanofibers. Helical carbon fibers are synthesized by a chemical vapor deposition process on a C-60 supported Pd catalyst and the obtained fibers are functionalized by H2O2 followed by a decoration with Pd nanoparticles. Although transmission electron microscopy images show that the decoration is relatively inhomogeneous the electrocatalytic activity for formic acid oxidation is very high. Cyclic voltammetry measurements (CV) show that the generated current peak value for Pd-decorated helical carbon nanofibers is 300 mA/mg(Pd) for a scan rate of 10 mV/s. This is significantly higher than the corresponding value of a reference sample of multiwalled carbon nanotubes decorated with Pd nanoparticles by the same process. Fuel cell tests for our Pd-decorated helical carbon nanofibers also displayed a high power density, although not as superior to Pd-decorated multiwalled nanotubes as measured by CV. Our results show that helical carbon nanofibers have several good properties, such as a rigid anchoring of catalyst nanoparticles and a suitable structure for creating functionalization defects which make them an interesting candidate for electrochemical applications. 

  • 52. Oltean, Gabriel
    et al.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Edström, Kristina
    Nyholm, Leif
    On the origin of the capacity fading for aluminium negative electrodes in Li-ion batteries2014In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 269, p. 266-273Article in journal (Refereed)
    Abstract [en]

    The origin of the capacity loss for aluminium negative electrodes in Li-ion batteries has been studied for electrodeposited aluminium nanorod electrodes coated with Al2O3 layers of different thicknesses (i.e. a native oxide layer, 30 and 60 nm) mainly employing pouch cell voltammetric cycling versus metallic lithium. Whereas the capacity decreased continuously during cycling between 0.1 and 3 V vs. Li+/Li, good cycling stability was obtained when the cycling was carried out between 0.1 and 1 V vs. Li+/Li. Since no significant dependence of the cycling stability on the thickness of the alumina layer was found in any of the experiments, the observed loss of capacity is unlikely to have been caused by volume expansion effects. The latter is further supported by the finding that the capacity (obtained when cycling between 0.1 and 3 V vs. Li+/Li) decreased linearly with the inverse of the square root of the cycling time, indicating that the capacity loss was due to the loss of lithium as a result of lithium diffusion into the bulk of the aluminium electrodes. The latter is explained based on a lithium-aluminium alloying and dealloying model which complements previously published models.

  • 53. Palo-Nieto, Carlos
    et al.
    Afewerki, Samson
    Anderson, Mattias
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Berglund, Per
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Mid Sweden University, Sweden.
    Integrated Heterogeneous Metal/Enzymatic Multiple Relay Catalysis for Eco-Friendly and Asymmetric Synthesis2016In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 6, no 6, p. 3932-3940Article in journal (Refereed)
    Abstract [en]

    Organic synthesis is in general performed using stepwise transformations where isolation and purification of key intermediates is often required prior to further reactions. Herein we disclose the concept of integrated heterogeneous metal/enzymatic multiple relay catalysis for eco-friendly and asymmetric synthesis of valuable molecules (e.g., amines and amides) in one-pot using a combination of heterogeneous metal and enzyme catalysts. Here reagents, catalysts, and different conditions can be introduced throughout the one-pot procedure involving multistep catalytic tandem operations. Several novel cocatalytic relay sequences (reductive amination/amidation, aerobic oxidation/reductive amination/amidation, reductive amination/kinetic resolution and reductive amination/ dynamic kinetic resolution) were developed. They were next applied to the direct synthesis of various biologically and optically active amines or amides in one-pot from simple aldehydes, ketones, or alcohols, respectively.

  • 54. Polido Legaria, Elizabeth
    et al.
    Rocha, Joao
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kessler, Vadim G.
    Seisenbaeva, Gulaim A.
    Unusual seeding mechanism for enhanced performance in solid-phase magnetic extraction of Rare Earth Elements2017In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 43740Article in journal (Refereed)
    Abstract [en]

    Due to the increasing demand of Rare Earth Elements (REE or RE), new and more efficient techniques for their extraction are necessary, suitable for both mining and recycling processes. Current techniques such as solvent extraction or solid adsorbents entail drawbacks such as using big volumes of harmful solvents or limited capacity. Hybrid nanoadsorbents based on SiO2 and highly stable gamma-Fe2O3-SiO2 nanoparticles, proved recently to be very attractive for adsorption of REE, yet not being the absolute key to solve the problem. In the present work, we introduce a highly appealing new approach in which the nanoparticles, rather than behaving as adsorbent materials, perform as inducers of crystallization for the REE in the form of hydroxides, allowing their facile and practically total removal from solution. This induced crystallization is achieved by tuning the pH, offering an uptake efficiency more than 20 times higher than previously reported (up to 900 mg RE3+/g vs. 40 mg RE3+/g). The obtained phases were characterized by SEM-EDS, TEM, STEM and EFTEM and C-13 and Si-29 solid state NMR. Magnetic studies showed that the materials possessed enough magnetic properties to be easily removed by a magnet, opening ways for an efficient and industrially applicable separation technique.

  • 55. Qi, Kezhen
    et al.
    Selvaraj, Rengaraj
    Al Fahdi, Tharaya
    Al-Kindy, Salma
    Kim, Younghun
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Sillanpää, Mika
    Hierarchical alpha-MnS microspheres: Solvothermal synthesis and growth mechanism2016In: Materials letters (General ed.), ISSN 0167-577X, E-ISSN 1873-4979, Vol. 166, p. 116-120Article in journal (Refereed)
    Abstract [en]

    Hierarchical-like alpha-MnS microspheres have been successfully synthesized via a simple solvothermal route using L-Cystein as both sulfur source and capping agent. X-ray diffraction (XRD) analysis confirmed that these hierarchical microspheres were made of alpha-phase MnS. Morphological studies performed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) methods showed that the alpha-MnS hierarchical microspheres are obtained from the nanocubes by self-assembly due to the main driving force of the minimization of overall surface energy. It is highly expected this research can provide a useful fundamental understanding of shape-controlled synthesis of the semiconductor material with hierarchical microstructures.

  • 56. Qi, Kezhen
    et al.
    Selvaraj, Rengaraj
    Al Fahdi, Tharaya
    Al-Kindy, Salma
    Kim, Younghun
    Wang, Gui-Chang
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Sillanpää, Mika
    Enhanced photocatalytic activity of anatase-TiO2 nanoparticles by fullerene modification: A theoretical and experimental study2016In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 387, p. 750-758Article in journal (Refereed)
    Abstract [en]

    A series of fullerene (C-60)-modified anatase TiO2 (a-TiO2) nanocomposites with different weight loadings of C-60 were successfully synthesized by a simple solution phase method. The as-prepared C-60@a-TiO2 nanocomposites were characterized by X-ray diffraction (XRD), Raman spectroscopy, Brunauer-Emmett-Teller (BET), UV-vis diffuse reflectance absorption spectra (DRS), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS). The photocatalytic degradation of methylene blue (MB) by the neat a-TiO2 and C-60@a-TiO2 nanocomposites was investigated under UV-A light irradiation, demonstrating that C-60 effectively enhances the photocatalytic activity of a-TiO2 nanoparticles with an optimal amount of 2.0 wt%. By combining with the density functional theory (DFT) calculations, we investigated the electronic structures of C-60@a-TiO2 hetero-interfaces to reveal the underlying principle of the C-60 loading on the photocatalytic activity. It was found that the incorporation of C-60 on the a-TiO2 surface not only narrowed the band gap, but also introduced an additional doping state between the valance and conduction band. Therefore, the presence of intermediate electronic state will in turn contribute to the efficient charge separation and enhanced light adsorption for the C-60@a-TiO2 nanocomposites, resulting in an improved photocatalytic performance.

  • 57.
    Qi, Kezhen
    et al.
    Shenyang Normal University, Shenyang, China.
    Selvaraj, Rengaraj
    Sultan Qaboos University, Muscat, Sultanate of Oman.
    Jeong, Uiseok
    Kwangwoon University, Korea .
    Al-Kindy, Salma M. Z.
    Sultan Qaboos University, Muscat, Sultanate of Oman.
    Sillanpää, Mika
    Lappeenranta University of Technology, FInland.
    Kim, Younghun
    Kwangwoon University, Korea.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hierarchical-like multipod γ-MnS microcrystals: solvothermal synthesis, characterization and growth mechanism2015In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 5, no 13, p. 9618-9620Article in journal (Refereed)
    Abstract [en]

    Novel hierarchical multipod gamma-MnS microcrystals have been successfully synthesized by a simple solvothermal method, in which manganese acetate was used as a manganese source and thiosemicarbazide was used as both sulfur source and capping agent.

  • 58. Qiu, Zhen
    et al.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Niklasson, Gunnar A.
    Edvinsson, Tomas
    Direct observation of active catalyst surface phases and the effect of dynamic self-optimization in NiFe-layered double hydroxides for alkaline water splitting2019In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 12, no 2, p. 572-581Article in journal (Refereed)
    Abstract [en]

    Earth-abundant transition metal-based compounds are of high interest as catalysts for sustainable hydrogen fuel generation. The realization of effective electrolysis of water, however, is still limited by the requirement of a high sustainable driving potential above thermodynamic requirements. Here, we report dynamically self-optimized (DSO) NiFe layered double hydroxide (LDH) nanosheets with promising bi-functional performance. Compared with pristine NiFe LDH, DSO NiFe LDH exhibits much lower overpotential for the hydrogen evolution reaction (HER), even outperforming platinum. Under 1 M KOH aqueous electrolyte, the bi-functional DSO catalysts show an overpotential of 184 and -59 mV without iR compensation for oxygen evolution reaction (OER) and HER at 10 mA cm(-2). The material system operates at 1.48 V and 1.29 V to reach 10 and 1 mA cm(-2) in two-electrode measurements, corresponding to 83% and 95% electricity-to-fuel conversion efficiency with respect to the lower heating value of hydrogen. The material is seen to dynamically reform the active phase of the surface layer during HER and OER, where the pristine and activated catalysts are analyzed with ex situ XPS, SAED and EELS as well as with in situ Raman spectro-electrochemistry. The results show transformation into different active interfacial species during OER and HER, revealing a synergistic interplay between iron and nickel in facilitating water electrolysis.

  • 59. Raudonyte-Svirbutaviciene, Eva
    et al.
    Neagu, Alexandra
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Vickackaite, Vida
    Jasulaitiene, Vitalija
    Zarkov, Aleksej
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Katelnikovas, Arturas
    Two-step photochemical inorganic approach to the synthesis of Ag-CeO2 nanoheterostructures and their photocatalytic activity on tributyltin degradation2018In: Journal of Photochemistry and Photobiology A: Chemistry, ISSN 1010-6030, E-ISSN 1873-2666, Vol. 351, p. 29-41Article in journal (Refereed)
    Abstract [en]

    Herein, we report a simple, sustainable and low-cost approach to design Ag-CeO2 nanoheterostructures in pure aqueous and ethanol containing aqueous solutions via photochemical UV-light driven process with no capping agents nor stabilizers required. To this end, photochemically synthesized CeO2 nanoparticles were applied as photoactive compounds in order to generate formation of metallic silver nanoparticles. Irradiation of deaerated CeO2 suspensions in the presence of Ag+ resulted in the rise of a strong surface plasmon resonance band with a maximum at 393-422 nm in the absorption spectra of the solutions, indicating formation of small metallic silver particles. Faster formation of Ag nanoparticles with the lower amount of silver precursor being required was observed when ethanol was introduced to the reaction solution before the irradiation. This implies that oxidative reactions can be strongly suppressed in deaerated ethanol containing solutions with respect to the pure aqueous media. Not only was the overall efficiency of the process remarkably increased by the use of alcohol, but also smaller and more uniform silver nanoparticles with a size comparable to that of ceria nanoparticles (around 15 nm) were formed when compared to those synthesized without radical scavengers as revealed by TEM analysis. The proposed photochemical approach enables the production of silver-semiconductor system without employing organic stabilizers, thus resulting in formation of nanoparticles with clean, highly reactive metal surface. The as-synthesized silver-ceria nanoheterostructures demonstrated enhanced visible light driven photocatalytic activity on tributyltin (TBT) degradation if compared to pure ceria nanoparticles.

  • 60. Rehnlund, David
    et al.
    Valvo, Mario
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Ångström, Jonas
    Sahlberg, Martin
    Edström, Kristina
    Nyholm, Leif
    Electrochemical fabrication and characterization of Cu/Cu2O multi-layered micro and nanorods in Li-ion batteries2015In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 7, no 32, p. 13591-13604Article in journal (Refereed)
    Abstract [en]

    Electrodes composed of freestanding nano- and microrods composed of stacked layers of copper and cuprous oxide have been fabricated using a straightforward one-step template-assisted pulsed galvanostatic electrodeposition approach. The approach provided precise control of the thickness of each individual layer of the high-aspect-ratio rods as was verified by SEM, EDS, XRD, TEM and EELS measurements. Rods with diameters of 80, 200 and 1000 nm were deposited and the influence of the template pore size on the structure and electrochemical performance of the conversion reaction based electrodes in lithium-ion batteries was investigated. The multi-layered Cu2O/Cu nano-and microrod electrodes exhibited a potential window of more than 2 V, which was ascribed to the presence of a distribution of Cu2O (and Cu, respectively) nanoparticles with different sizes and redox potentials. As approximately the same areal capacity was obtained independent of the diameter of the multi-layered rods the results demonstrate the presence of an electroactive Cu2O layer with a thickness defined by the time domain of the measurements. It is also demonstrated that while the areal capacity of the electrodes decreased dramatically when the scan rate was increased from 0.1 to 2 mV s(-1), the capacity remained practically constant when the scan rate was further increased to 100 mV s(-1). This behaviour can be explained by assuming that the capacity is limited by the lithium ion diffusion rate though the Cu2O layer generated during the oxidation step. The electrochemical performance of present type of 3-D multi-layered rods provides new insights into the lithiation and delithiation reactions taking place for conversion reaction materials such as Cu2O.

  • 61. Rengaraj, Selvaraj
    et al.
    Venkataraj, Selvaraj
    Jee, Sun Hee
    Kim, Younghun
    Tai, Cheuk-wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Repo, Eveliina
    Koistinen, Arto
    Ferancova, Adriana
    Sillanpaa, Mika
    Cauliflower-like CdS Microspheres Composed of Nanocrystals and Their Physicochemical Properties2011In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, no 1, p. 352-358Article in journal (Refereed)
    Abstract [en]

    Cauliflower-like cadmium sulfide (CdS) microspheres composed of nanocrystals have been successfully synthesized by a hydrothermal method using poly(ethylene glycol) (PEG) as the template coordination agent and characterized by a variety of methods. Our experiments confirmed that the size of the CdS microspheres could be easily modified by controlling the chain length of PEG. Powder X-ray diffraction and Raman spectroscopy measurements revealed the cubic structure of the CdS microspheres; morphological studies performed by HR-SEM and HR-TEM methods showed the cauliflower-like structure of the synthesized CdS microspheres. Each microsphere was identified to be created by the self-assembly of CdS nanocrystals and is attributed to the oriented aggregation of the CdS nanocrystals around a polymer-Cd(2+) complex spherical framework structure. X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray (EDX) analysis confirmed the stoichiometries of the CdS microspheres. Diffuse reflectance spectrum (DRS) measurements showed that increasing the PEG chain length increased the band gap value of the CdS microspheres slightly, from 1.99 to 2.06 eV. The cauliflower-like CdS microspheres could be applied to photocatalytic degradation studies.

  • 62. Rengaraj, Selvaraj
    et al.
    Venkataraj, Selvaraj
    Tai, Cheuk-wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kim, Younghun
    Repo, Eveliina
    Sillanpaa, Mika
    Self-Assembled Mesoporous Hierarchical-like In(2)S(3) Hollow Microspheres Composed of Nanofibers and Nanosheets and Their Photocatalytic Activity2011In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, no 9, p. 5534-5541Article in journal (Refereed)
    Abstract [en]

    Novel template-free hierarchical-like In(2)S(3) hollow microspheres were synthesized using thiosemicarbazide (NH(2)NHCSNH(2)) as both a sulfur source and a capping ligand in a ethanol/water system. In this study, we demonstrate that several process parameters, such as the reaction time and precursor ratio, strongly influence the morphology of the final product. The In(NO(3))(3)/thiosemicarbazide ratios were found to effectively play crucial roles in the morphologies of the hierarchical-like In(2)S(3) hollow microsphere nanostructure. With the ratios increasing from two to four, the In(2)S(3) crystals exhibited almost spherical morphologies. The synthesized products have been characterized by a variety of methods, including X-ray powder diffraction (XRD), Raman spectroscopy, field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray (EDX) analysis, X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible diffused reflectance spectroscopy (UV-vis DRS). XRD analysis confirmed the tetragonal structure of the In(2)S(3) hollow microspheres. The products show complex hierarchical structures assembled from nanoscale building blocks. The morphology evolution can be realized on both outside (surface) and inside (hollow cavity) the microsphere. The surface area analysis showed that the porous In(2)S(3) possesses a specific surface area of 108 m(2)/g and uniform distribution of pore sizes corresponding to the size of pores resulting from the self-assembled structures with flakes. The optical properties of In(2)S(3) were also investigated by UV-vis DRS, which indicated that our In(2)S(3) microsphere samples possess a band gap of similar to 1.96 eV. Furthermore, the photocatalytic activity studies revealed that the synthesized In(2)S(3) hollow microspheres exhibit an excellent photocatalytic performance in rapidly degrading aqueous methylene blue dye solution under visible light irradiation. These results suggest that In(2)S(3) hollow microspheres will be an interesting candidate for photocatalytic detoxification studies under visible light radiation.

  • 63. Renman, Viktor
    et al.
    Valvo, Mario
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Gomez, Cesar Pay
    Edstrom, Kristina
    Liivat, Anti
    Manganese pyrosilicates as novel positive electrode materials for Na-ion batteries2018In: sustainable energy and fuels, ISSN 2398-4902, Vol. 2, no 5, p. 941-945Article in journal (Refereed)
    Abstract [en]

    A carbon-coated pyrosilicate, Na2Mn2Si2O7/C, was synthesized and characterized for use as a new positive-electrode material for sodium ion batteries. The material consists of 20-80 nm primary particles embedded in a approximate to 10 nm-thick conductive carbon matrix. Reversible insertion of Na+ ions is clearly demonstrated with approximate to 25% of its theoretical capacity (165 mA h g(-1)) being accessible at room temperature at a low cycling rate. The material yields an average potential of 3.3 V vs. Na+/Na on charge and 2.2 V on discharge. DFT calculations predict an equilibrium potential for Na2Mn2Si2O7 in the range of 2.8-3.0 V vs. Na+/Na, with a possibility of a complete flip in the connectivity of neighboring Mn-polyhedra - from edge-sharing to disconnected and vice versa. This significant rearrangement in Mn coordination (approximate to 2 angstrom) and large volume contraction (>10%) could explain our inability to fully desodiate the material, and illustrates well the need for a new electrode design strategy beyond the conventional down-sizing/coating procedure.

  • 64. Renman, Viktor
    et al.
    Valvo, Mario
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zimmermann, Iwan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Johnsson, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Gomez, Cesar Pay
    Edström, Kristina
    Investigation of the Structural and Electrochemical Properties of Mn2Sb3O6CI upon Reaction with Li Ions2017In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 11, p. 5949-5958Article in journal (Refereed)
    Abstract [en]

    The structural and electrochemical properties of a quaternary layered compound with elemental composition Mn2Sb3O6Cl have been investigated upon reaction with lithium in Li half cells. Operando XRD was used to investigate the potential impact of this particular layered structure on the lithiation process. Although the results suggest that the material is primarily reacted through a conventional conversion mechanism, they also provide some hints that the space between the slabs may act as preferential entry points for lithium ions but not for the larger sodium ions. Cyclic voltammetry, galvanostatic cycling, HRTEM, SAED, and EELS analyses were performed to unravel the details of the reaction mechanism with the lithium ions. It is found that two pairs of reactions are mainly responsible for the reversible electrochemical cycling of this compound, namely, the alloying of Li-Sb and the conversion of MnxOy to metallic Mn with concomitant formation of Li2O upon lithium uptake. A moderate cycling stability is achieved with a gravimetric capacity of 467 mAh g(-1) after 100 cycles between 0.05 and 2.2 V vs Li+/Li despite the large particle sizes of the active material and its nonoptimal inclusion into composite coatings. The electrochemical activity of the title compound was also tested in Na half cells between 0.05 and 2 V vs Ne/Na. It was found that a prolonged period of electrochemical milling is required to fully gain access to the active material, after which the cell delivers a capacity of 350 mAh CI. These factors are demonstrated to clearly limit the ultimate performances for these electrodes.

  • 65. Schitco, Cristina
    et al.
    Turdean-Ionescu, Claudia
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bazarjani, Mahdi Seifollahi
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Li, Duan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Fasel, Claudia
    Donner, Wolfgang
    Shen, James
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Riedel, Ralf
    Gurlo, Aleksander
    Edén, Mattias
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Silicon oxycarbonitrides synthesized by ammonia-assisted thermolysis route from polymers: A total X-ray scattering, solid-state NMR, and TEM structural study2016In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 35, no 4, p. 979-989Article in journal (Refereed)
    Abstract [en]

    Solid-state nuclear magnetic resonance (NMR) spectroscopy, total X-ray scattering with a pair distribution function (PDF) analysis, and transmission electron microscopy (TEM) were employed to explore the structures of microporous and non-porous ceramics synthesized by an NH3-assisted thermolysis from polymers. Polysiloxane (SPR-212a, Starfire® Systems) and polysilazane (HTT-1800, KiON Speciality Polymers) polymers form microporous silicon oxycarbonitride ceramics with accessible and tailored micropores. 29Si magic-angle-spinning NMR showed that the introduction of nitrogen leads to structures incorporating considerable amounts of SiN4 and SiO2N2 building blocks. The samples derived from a polycarbosilane (SMP-10, Starfire® Systems) remained non-porous: for such a C-rich and N-bearing phase, the NMR, TEM, and PDF results suggested a Si network exhibiting domains dominated by either SiN or SiC bonds. 13C NMR revealed primarily “carbidic” CSi4 environments in the C-rich phases, as well as the formation of an amorphous sp2-hybridized carbon phase; both are believed to be detrimental for the micropore formation.

  • 66. Selvaraj, Rengaraj
    et al.
    Qi, Kezhen
    Al-Kindy, Salma M. Z.
    Sillanpaa, Mika
    Kim, Younghun
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    A simple hydrothermal route for the preparation of HgS nanoparticles and their photocatalytic activities2014In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 4, no 30, p. 15371-15376Article in journal (Refereed)
    Abstract [en]

    HgS nanoparticles have been successfully prepared by a hydrothermal method using polyethylene glycol (PEG) as stabilizing agent and characterized by a variety of methods. Our experiments confirmed that the size of the HgS nanocrystals could be easily modified by tuning the chain length of PEG. X-ray powder diffraction (XRD) results for the nanoparticles revealed the hexagonal structure of the HgS, i. e. a-phase known as cinnabar. Morphological studies performed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that the synthesized nanocrystals were nanoparticles. Furthermore, a rational mechanism of the formation and evolution of the products was proposed. The optical properties of HgS were investigated by diffuse reflectance spectroscopy (DRS), which indicated that the band gap of the nanoparticles is slightly decreased from 2.05 to 2.00 eV as the average particle size decreases from 55 to 35 nm. Furthermore, the photocatalytic activity studies of the particles demonstrated their excellent photocatalytic performance in rapidly degrading aqueous methylene blue dye solution under visible light irradiation. These results suggest that HgS nanoparticles will be an interesting candidate of photocatalyst working in visible light range.

  • 67.
    Shakeri, Mozaffar
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Göthelid, Emmanuelle
    Oscarsson, Sven
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Small Pd Nanoparticles Supported in Large Pores of Mesocellular Foam: An Excellent Catalyst for Racemization of Amines2011In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 17, no 47, p. 13269-13273Article in journal (Refereed)
    Abstract [en]

    Highly dispersed palladium nanoparticles (1–2 nm) supported in large-pore mesocellular foam (MCF; 29 nm) were synthesized. The Pd-nanocatalyst/MCF system was characterized by transmission electron microscopy (TEM), powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The performance of the Pd nanocatalyst obtained was examined for amine racemization. The Pd nanocatalyst showed higher activity and selectivity toward racemization of (S)-1-phenylethyl amine than any other amine racemization catalyst reported so far and it could be reused several times. Our data from TEM and XRD suggest a restructuring of the Pd nanocatalyst from amorphous to crystalline and an increase in Pd nanocatalyst size during the racemization reaction. This led to an unexpected increase of activity after the first use. The Pd nanocatalyst obtained can be integrated with other resolving processes of racemic organic compounds to increase the yield of chiral organic products.

  • 68. Sharifi, Tiva
    et al.
    Gracia-Espino, Eduardo
    Barzegar, Hamid Reza
    Jia, Xueen
    Nitze, Florian
    Hu, Guangzhi
    Nordblad, Per
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Wågberg, Thomas
    Formation of nitrogen-doped graphene nanoscrolls by adsorption of magnetic gamma-Fe2O3 nanoparticles2013In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 4, p. 2319-Article in journal (Refereed)
    Abstract [en]

    Graphene nanoscrolls are Archimedean-type spirals formed by rolling single-layer graphene sheets. Their unique structure makes them conceptually interesting and understanding their formation gives important information on the manipulation and characteristics of various carbon nanostructures. Here we report a 100% efficient process to transform nitrogen-doped reduced graphene oxide sheets into homogeneous nanoscrolls by decoration with magnetic gamma-Fe2O3 nanoparticles. Through a large number of control experiments, magnetic characterization of the decorated nanoparticles, and ab initio calculations, we conclude that the rolling is initiated by the strong adsorption of maghemite nanoparticles at nitrogen defects in the graphene lattice and their mutual magnetic interaction. The nanoscroll formation is fully reversible and upon removal of the maghemite nanoparticles, the nanoscrolls return to open sheets. Besides supplying information on the rolling mechanism of graphene nanoscrolls, our results also provide important information on the stabilization of iron oxide nanoparticles.

  • 69. Sharifi, Tiva
    et al.
    Nitze, Florian
    Barzegar, Hamid Reza
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Mazurkiewicz, Marta
    Malolepszy, Artur
    Stobinski, Leszek
    Wagberg, Thomas
    Nitrogen doped multi walled carbon nanotubes produced by CVD-correlating XPS and Raman spectroscopy for the study of nitrogen inclusion2012In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 50, no 10, p. 3535-3541Article in journal (Refereed)
    Abstract [en]

    High purity aligned nitrogen doped multi walled carbon nanotubes were synthesized by the catalytic chemical vapor deposition method using pyridine and Fe/Co (2:1 volume ratio) as the single C/N precursor and catalyst material. The average diameter of the synthesized tubes ranges between 29 nm and 57 nm and the nitrogen content of the tubes reaches a maximum of 9.2 (at.)% nitrogen. The effect of nitrogen doping on the Raman scattering of doped tubes and its correlation with X-ray photoelectron spectra (XPS) was investigated. The analysis is based on the investigation of the I-D/I-G (integrated area ratio), other nitrogen characteristic Raman modes and the type of nitrogen inclusion interpreted from the N 1s electron bonding energies in XPS. At doping levels higher than 5% the nitrogen inclusion takes place through another mechanism than at low nitrogen doping levels. Most significant is that pyridinic defects are relatively readily incorporated at low nitrogen doping levels while at nitrogen content higher than 5% the major incorporation mechanism is dominated by pyridinic and pyrrolic defects on an equal basis. Our study gives further insight into nitrogen doping effects and the relation between type of nitrogen inclusion and nitrogen doping levels.

  • 70. Shi, Liyang
    et al.
    Zeng, Yuqin
    Zhao, Yannan
    Yang, Bin
    Ossipov, Dmitri
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Dai, Jianwu
    Xu, Changgang
    Biocompatible Injectable Magnetic Hydrogel Formed by Dynamic Coordination Network2019In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 11, no 49, p. 46233-46240Article in journal (Refereed)
    Abstract [en]

    Magnetic hydrogel that can respond to a magnetic stimulus is a promising biomaterial for tissue regeneration and cancer treatment. In this study, a novel magnetic hydrogel is formed by simply mixing bisphosphonate (BP)-modified hyaluronic acid (i.e., HA-BP) polymeric solution and iron oxide (Fe3O4) nanoparticle dispersion, in which the hydrogel networks are cross linked by BP groups and iron atoms on the surface of particle. The iron BP coordination chemistry affords a dynamic network, characterized by self-healing, shear-thinning, and smoothly injectable properties. Moreover, the HA-BP-Fe3O4 magnetic hydrogel demonstrates heat-generation characterization under an alternating magnetic field. The animal experiments confirm the biocompatibilities of HA BP center dot Fe3O4 hydrogel, which presents the hydrogels potential for tissue regeneration and anticancer treatment applications.

  • 71. Sobkowiak, Adam
    et al.
    Roberts, Matthew R.
    Younesi, Reza
    Ericsson, Tore
    Häggström, Lennart
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Anderssor, Anna M.
    Edström, Kristina
    Gustafsson, Torbjörn
    Björefors, Fredrik
    Understanding and Controlling the Surface Chemistry of LiFeSO4F for an Enhanced Cathode Functionality2013In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 25, no 15, p. 3020-3029Article in journal (Refereed)
    Abstract [en]

    The tavorite polymorph of LiFeSO4F has recently attracted a lot of interest as a cathode material for lithium ion batteries stimulated by its competitive specific capacity, high potential for the Fe2+/Fe3+ redox couple, and low-temperature synthesis. However, the synthesis routes explored to date have resulted in notably varied electrochemical performance. This inconsistency is difficult to understand given the excellent purity, crystallinity, and similar morphologies achieved via all known methods. In this work, we examine the role of the interfacial chemistry on the electrochemical functionality of LiFeSO4F. We demonstrate that particularly poor electrochemical performance may be obtained for pristine materials synthesized in tetraethylene glycol (TEG), which represents one of the most economically viable production methods. By careful surface characterization, we show that this restricted performance can be largely attributed to residual traces of TEG remaining on the surface of pristine materials, inhibiting the electrochemical reactions. Moreover, we show that optimized cycling performance of LiFeSO4F can be achieved by removing the unwanted residues and applying a conducting polymer coating, which increases the electronic contact area between the electrode components and creates a highly percolating network for efficient electron transport throughout the composite material. This coating is produced using a simple and scalable method designed to intrinsically favor the functionality of the final product.

  • 72.
    Stingaciu, Marian
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Reuvekamp, P. G.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kremer, R. K.
    Johnsson, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    The magnetodielectric effect in BaTiO3-SrFe12O19 nanocomposites2014In: Journal of Materials Chemistry C: Materials for Optical and Electronic Devices, ISSN 2050-7526, Vol. 2, no 2, p. 325-330Article in journal (Refereed)
    Abstract [en]

    A nanoscale composite consisting of 30 vol% magnetic strontium hexaferrite SrFe12O19 embedded in a high dielectric permittivity matrix of BaTiO3 has been produced by the spark plasma sintering method. The morphology and phase composition were characterized by transmission electron microscopy (TEM) and powder X-ray diffraction (XRD) techniques. TEM micrographs indicate that no considerable grain growth occurs and different strained regions were formed by the sintering process. XRD investigations show no evidence of a chemical reaction between the constituents. The dielectric properties of such a nanocomposite were investigated versus temperature (50-300 K), frequency (100 Hz to 100 kHz) and magnetic field (0-5.6 Tesla). A magnetodielectric (MD) effect was detected in the whole studied temperature range. Above 150 K the occurrence of sharp magnetodielectric resonances around 1 kHz leads to a considerable enhancement of the effect. At temperatures below 150 K a positive MD effect was detected which is independent of the frequency.

  • 73. Sun, Rui
    et al.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Strømme, Maria
    Cheung, Ocean
    Hierarchical Porous Carbon Synthesized from Novel Porous Amorphous Calcium or Magnesium Citrate with Enhanced SF6 Uptake and SF6/N-2 Selectivity2019In: Acs Applied Nano Materials, ISSN 2574-0970, Vol. 2, no 2, p. 778-789Article in journal (Refereed)
    Abstract [en]

    The emission of greenhouse gases such as CO2 and SF6 is believed to contribute significantly toward global warming. One way to reduce their release is by adsorption at point sources using a suitable adsorbent. In this work we present the synthesis of two hierarchical porous carbon materials (referred to as PC-CaCit and PC-MgCit) with a high uptake of SF 6 (5.23 mmol/g, 0 degrees C, 100 kPa) and a reasonable uptake of CO2 (>3 mmol/g). PC-CaCit and PC-MgCit were obtained by pyrolysis of the most porous calcium citrate and magnesium citrate ever reported, which were synthesized by us. The Langmuir specific surface area of PC-CaCit and PC-MgCit was over 2000 m(2)/g (BET surface area also close to 2000 m(2)/g). We characterized PC-CaCit and PC-MgCit using a range of advanced characterization techniques including N-2 adsorption, high-resolution electron microscopy, powder X-ray diffraction, and X-ray photoelectron spectroscopy. PC-CaCit and PC-MgCit also showed a SF6-over-N-2 selectivity of similar to 33 at 0 degrees C (100 kPa), good cyclic performance, and moderately low heat of adsorption. The porous carbons synthesized in this work are good candidate adsorbents for greenhouse gases.

  • 74. Sun, Rui
    et al.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Strømme, Maria
    Cheung, Ocean
    The effects of additives on the porosity and stability of amorphous calcium carbonate2019In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 292, article id 109736Article in journal (Refereed)
    Abstract [en]

    Amorphous calcium carbonate (ACC) stabilized by various carboxylic additives was synthesized by incorporating the additives into an ACC suspension in methanol. The additives studied included polyacrylic acid, citric acid, adipic acid, 6-aminocaproic acid, 4-aminobutyric acid and hexanoic acid. The stabilized ACC samples (ACC-additives) exhibited similar characteristics to ACC alone. They appeared X-ray amorphous, contained characteristic infrared bands and had the same nanoparticle aggregated microstructure as ACC. The porosity of the ACC-additives was, however, markedly improved, with Brimauer-Emmett-Teller (BET) surface areas of up to similar to 640 m(2)/g. The BET surface area of ACC-citric acid was close to double that of a highly porous ACC sample. The structure and amount of the additive had a noticeable effect on the porosity of the ACC-additives. When the additive was adsorbed onto the surface of the ACC nanoparticles, their growth was restricted. The restricted growth reduced the size of the ACC nanoparticles, which increased the BET surface area of ACC. Finally, the long-term stability study revealed that the stability of all the ACC-additives was markedly enhanced when stored in ambient or semi-airtight conditions (in a closed falcon tube). In particular, ACC stabilized with adipic acid (ACC-AA-267) had excellent stability, remaining in an amorphous phase for more than one year under ambient conditions and retaining similar to 87% porosity for 48 weeks under semi-airtight conditions. The extremely high porosity and excellent long-term stability make these ACC-additives promising candidates for applications where porosity and stability are critical, such as those involving adsorption, bone regeneration or drug delivery.

  • 75. Sun, Rui
    et al.
    Zhang, Peng
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Uppsala University, Sweden.
    Bajnócz, Éva G.
    Neagu, Alexandra
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Persson, Ingmar
    Strømme, Maria
    Cheung, Ocean
    Amorphous Calcium Carbonate Constructed from Nanoparticle Aggregates with Unprecedented Surface Area and Mesoporosity2018In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, no 25, p. 21556-21564Article in journal (Refereed)
    Abstract [en]

    Amorphous calcium carbonate (ACC), with the highest reported specific surface area of all current forms of calcium carbonate (over 350 m(2) g(-1)), was synthesized using a surfactant-free, one-pot method. Electron microscopy, helium pycnometry, and nitrogen sorption analysis revealed that this highly mesoporous ACC, with a pore volume of similar to 0.86 cm(3) g(-1) and a pore-size distribution centered at 8-9 nm, is constructed from aggregated ACC nanoparticles with an estimated average diameter of 7.3 nm. The porous ACC remained amorphous and retained its high porosity for over 3 weeks under semi-air-tight storage conditions. Powder X-ray diffraction, large-angle X-ray scattering, infrared spectroscopy, and electron diffraction exposed that the porous ACC did not resemble any of the known CaCO3 structures. The atomic order of porous ACC diminished at interatomic distances over 8 angstrom. Porous ACC was evaluated as a potential drug carrier of poorly soluble substances in vitro. Itraconazole and celecoxib remained stable in their amorphous forms within the pores of the material. Drug release rates were significantly enhanced for both drugs (up to 65 times the dissolution rates for the crystalline forms), and supersaturation release of celecoxib was also demonstrated. Citric acid was used to enhance the stability of the ACC nanoparticles within the aggregates, which increased the surface area of the material to over 600 m(2) g(-1). This porous ACC has potential for use in various applications where surface area is important, including adsorption, catalysis, medication, and bone regeneration.

  • 76. Sun, Rui
    et al.
    Åhlén, Michelle
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bajnóczi, Éva G.
    de Kleijne, Fenne
    Ferraz, Natalia
    Persson, Ingmar
    Strømme, Maria
    Cheung, Ocean
    Highly Porous Amorphous Calcium Phosphate for Drug Delivery and Bio-Medical Applications2020In: Nanomaterials, E-ISSN 2079-4991, Vol. 10, no 1, article id 20Article in journal (Refereed)
    Abstract [en]

    Amorphous calcium phosphate (ACP) has shown significant effects on the biomineralization and promising applications in bio-medicine. However, the limited stability and porosity of ACP material restrict its practical applications. A storage stable highly porous ACP with Brunauer-Emmett-Teller surface area of over 400 m(2)/g was synthesized by introducing phosphoric acid to a methanol suspension containing amorphous calcium carbonate nanoparticles. Electron microscopy revealed that the porous ACP was constructed with aggregated ACP nanoparticles with dimensions of several nanometers. Large angle X-ray scattering revealed a short-range atomic order of <20 angstrom in the ACP nanoparticles. The synthesized ACP demonstrated long-term stability and did not crystallize even after storage for over 14 months in air. The stability of the ACP in water and an alpha-MEM cell culture medium were also examined. The stability of ACP could be tuned by adjusting its chemical composition. The ACP synthesized in this work was cytocompatible and acted as drug carriers for the bisphosphonate drug alendronate (AL) in vitro. AL-loaded ACP released 25% of the loaded AL in the first 22 days. These properties make ACP a promising candidate material for potential application in biomedical fields such as drug delivery and bone healing.

  • 77. Svensson, Fredric G. G.
    et al.
    Daniel, Geoffrey
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Seisenbaeva, Gulaim A. A.
    Kessler, Vadim G. G.
    Titanium phosphonate oxo-alkoxide clusters: solution stability and facile hydrolytic transformation into nano titania2020In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 10, no 12, p. 6873-6883Article in journal (Refereed)
    Abstract [en]

    Titanium (oxo-) alkoxide phosphonate complexes were synthesized using different titanium precursors and tert-butylphosphonic acid (tBPA) as molecular models for interaction between phosphonates and titania surfaces and to investigate the solution stability of these species. Reflux of titanium(iv) ethoxide or titanium(iv)(diisopropoxide)bis(2,4-pentadionate) with tert-butylphosphonic acid in toluene-ethanol mixture or acetone yielded seven titanium alkoxide phosphonate complexes; [Ti-5(mu(3)-O)(mu(2)-O)(mu-HOEt)(2)(mu-OEt)(3)(mu(2)-OEt)(mu(3)-tBPA)(3)(mu(3)-HtBPA)(mu(2)-tBPA)(2)(mu(2)-HtBPA)]center dot 3EtOH, 1, [Ti4O(mu-OEt)(5)(mu(2)-OEt)(7)(mu(3)-tBPA)], 2, [Ti-4(mu(2)-O)(2)(mu-OEt)(2)(mu-HOEt)(2)(mu(2)-tPBA)(2)(mu(2)-HtPBA)(6)]center dot 4EtOH, 3, [Ti-4(mu(2)-O)(2)(mu-OEt)(2)(mu-HOEt)(2)(mu(2)-tPBA)(2)(mu(2)-HtPBA)(6)]center dot 2EtOH, 4, [Ti-6(mu(2)-O)(mu(3)-O)(2)(mu(2)-OEt)(5)(mu-OEt)(6)(mu(3)-tBPA)(3)(mu(3)-HtBPA)], 5, [Ti-4(mu-(OPr)-O-i)(4)(acac)(4)(mu(2)-tBPA)(4)], 6 and [Ti-5(mu(4)-O)(mu(2)-O)(3)(mu(2)-OEt)(4)(mu-OEt)(6)(mu-HOEt)(mu(3)-tBPA)](2), 7. The binding mode of tBPA to the titanium oxo-core were either double or triple bridging or a combination of the two. No monodentate or chelating coordination was observed. P-31 NMR spectrometry of dissolved single crystals indicates that 1 and 5 retain their solid-state structures in solution, the latter even on moderate heating, while 6 and 7 dissolved into several other forms. The complexes were found to be sensitive towards hydrolysis, proceeding in a topotactic fashion with densification of the material into plates and lamellae resulting finally in core-shell nanoparticles with a crystalline core (anatase) and an amorphous outer shell upon contact with water at room temperature as observed by HRTEM and AFM analyses. P-31 NMR data supported degradation after addition of water to solutions of the complexes. Hydrolysis under different conditions affords complex oxide structures of different morphologies.

  • 78.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Diffuse scattering in Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3 relaxor solid solutions2013In: Microscopy and Microanalysis, ISSN 1431-9276, E-ISSN 1435-8115, Vol. 18, no 2, p. 1900-1901Article in journal (Refereed)
  • 79.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Ferroelectric domain morphology, electrical and electromechanical properties of Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 ceramics2011In: Ferroelectric and Multiferroic Materials, 2011Conference paper (Refereed)
    Abstract [en]

    Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 ceramics were fabricated by mixed-oxide route. The compositions along morphotropic phase boundary were investigated. Dielectric properties and piezoelectric coefficient were measured. The maximum relative permittivity is 33600 found in the (PIN-PT)x(PMN-PT)1-x ceramics with x = 0.1 at 167 °C. When increasing the amount of Pb(In1/2Nb1/2)O3, the piezoelectric coefficient of the ceramics decreases but the phase transition temperature increases. The selected-area electron diffraction patterns show the pseudo-cubic perovskite symmetry. Diffuse scattering is found in the diffraction pattern taken at higher order zone axis. Transmission electron microscopy study shows that the morphology of ferroelectric/ferroelastic domains is neither tetragonal nor rhombohedral configuration

  • 80.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Morphological study of soot particles by off-axis electron holography2010In: Proceedings of 17th International Microscopy Congress, Rio de Janeiro,Brazil, 2010, p. M22.2-Conference paper (Refereed)
    Abstract [en]

     

     

     

  • 81.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Oxygen octahedral tilting and ferroelectric domain morphology in lead-free Bi1/2Na1/2TiO3-Bi1/2K1/2TiO3-BaTiO3 ceramics2010In: Proceedings of the 17th International Microscopy Congress, Rio de Janeiro, Brazil, 2010, p. M9.12-1-M9.12-2Conference paper (Refereed)
    Abstract [en]

     

     

  • 82.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Synthesis and characterization of carbon nanotubes decorated with gold nanoparticles2010In: Acta Physica Polonica. A, ISSN 0587-4246, E-ISSN 1898-794X, Vol. 118, no 3, p. 483-486Article in journal (Refereed)
    Abstract [en]

    In presented work we report results of simple and viable method for producing Au/CNT composites. Chemicalcomposition and crystallographic structure of the Au/CNT composites was confirmed by X-ray diffractionmeasurements, while transmission and scanning electron microscopy were used to characterize the morphology ofnanocrystals as well as the distribution of nanocrystals in the composite. The obtained particles with relativelysmall diameter (less than 9 nm) were found to be spatially well dispersed on the carbon nanotubes. The densityof attached Au–nanoparticles is not sufficient, and cannot be improved by simple increasing gold loading.

  • 83.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    TEM sample preparation by facile ion-milling - Ion Slicer2014Conference paper (Other academic)
  • 84.
    Tai, Cheuk-Wai
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Santosh, Mysore Sridhar
    Microwave assisted systhesis and magnetics studies of cobalt oxide nanoparticles2010In: Materials Chemistry and Physics, ISSN 0254-0584, E-ISSN 1879-3312, Vol. 125, p. 347-350Article in journal (Refereed)
    Abstract [en]

    An efficient microwave-assisted route has been used to synthesize nanoparticles of cobalt oxide. The particles were well characterized by transmission electron microscopy (TEM) which showed that the average diameter of the particles is around 6 nm. X-ray diffraction (XRD) studies further confirmed the formation of the spinel Co3O4. Purity of the products was detected by Fourier transform infrared spectroscopy (FTIR) combined with thermal gravimetric analysis (TG/DTG). The magnetic measurements revealed a small hysteresis loop at room temperature indicating a weak ferromagnetic nature of the synthesized Co3O4 nanoparticles. The magnetic moment of the particles was measured to be 4.27 μeff.

  • 85. Talyzin, A. V.
    et al.
    Luzan, S. M.
    Leifer, K.
    Akhtar, S.
    Fetzer, J.
    Cataldo, F.
    Tsybin, Y. O.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Dzwilewski, A.
    Moons, E.
    Coronene Fusion by Heat Treatment: Road to Nanographenes2011In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 27, p. 13207-13214Article in journal (Refereed)
    Abstract [en]

    The reactions of coronene dehydrogenation and fusion upon heat treatment in the temperature range of 500-700 degrees C were studied using XRD, TEM, Raman, IR, and NEXAFS spectroscopy. The formation of a coronene dimer (dicoronylene) was observed at temperatures 530-550 degrees C; dicoronylene can easily be separated using sublimation with a temperature gradient. An insoluble and not sublimable black precipitate was found to form at higher temperatures. Analysis of the data shows that dimerization of coronene is followed at 550-600 degrees C by oligomerization into larger molecules. Above 600 degrees C amorphization of the material and formation of graphitic nanoparticles was observed. Coronene fusion by annealing is proposed as a road to synthesis of larger polycyclic aromatic hydrocarbons and nanographenes.

  • 86.
    Thersleff, Thomas
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Schönström, Linus
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Uppsala University, Sweden.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Adam, Roman
    Bürgler, Daniel E.
    Schneider, Claus M.
    Muto, Shunsuke
    Rusz, Ján
    Single-pass STEM-EMCD on a zone axis using a patterned aperture: progress in experimental and data treatment methods2019In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 18170Article in journal (Refereed)
    Abstract [en]

    Measuring magnetic moments in ferromagnetic materials at atomic resolution is theoretically possible using the electron magnetic circular dichroism (EMCD) technique in a (scanning) transmission electron microscope ((S)TEM). However, experimental and data processing hurdles currently hamper the realization of this goal. Experimentally, the sample must be tilted to a zone-axis orientation, yielding a complex distribution of magnetic scattering intensity, and the same sample region must be scanned multiple times with sub-atomic spatial registration necessary at each pass. Furthermore, the weak nature of the EMCD signal requires advanced data processing techniques to reliably detect and quantify the result. In this manuscript, we detail our experimental and data processing progress towards achieving single-pass zone-axis EMCD using a patterned aperture. First, we provide a comprehensive data acquisition and analysis strategy for this and other EMCD experiments that should scale down to atomic resolution experiments. Second, we demonstrate that, at low spatial resolution, promising EMCD candidate signals can be extracted, and that these are sensitive to both crystallographic orientation and momentum transfer.

  • 87.
    Tinnis, Fredrik
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Verho, Oscar
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Gustafson, Karl P. J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bäckvall, Jan-Erling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Adolfsson, Hans
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Efficient Palladium-Catalyzed Aminocarbonylation of Aryl Iodides Using Palladium Nanoparticles Dispersed on Siliceous Mesocellular Foam2014In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 20, no 20, p. 5885-5889Article in journal (Refereed)
    Abstract [en]

    A highly dispersed nanopalladium catalyst supported on mesocellular foam (MCF), was successfully used in the heterogeneous catalysis of aminocarbonylation reactions. During the preliminary evaluation of this catalyst it was discovered that the supported palladium nanoparticles exhibited a “release and catch” effect, meaning that a minor amount of the heterogeneous palladium became soluble and catalyzed the reaction, after which it re-deposited onto the support.

  • 88.
    Tran, Dung
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Svensson, Gunnar
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    TEM-based pair distribution function study of bimetallic nanoparticles2014In: XV International Conference on Electron Microscopy, 2014Conference paper (Other academic)
  • 89.
    Tran, Dung Trung
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Svensson, Gunnar
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    SUePDF: a program to obtain quantitative pair distribution functions from electron diffraction data2017In: Journal of applied crystallography, ISSN 0021-8898, E-ISSN 1600-5767, Vol. 50, p. 304-312Article in journal (Refereed)
    Abstract [en]

    SUePDF is a graphical user interface program written in MATLAB to achieve quantitative pair distribution functions (PDFs) from electron diffraction data. The program facilitates structural studies of amorphous materials and small nanoparticles using electron diffraction data from transmission electron microscopes. It is based on the physics of electron scattering as well as the total scattering methodology. A method of background modeling is introduced to treat the intensity tail of the direct beam, inelastic scattering and incoherent multiple scattering. Kinematical electron scattering intensity is scaled using the electron scattering factors. The PDFs obtained after Fourier transforms are normalized with respect to number density, nanoparticle form factor and the non-negativity of probability density. SUePDF is distributed as free software for academic users.

  • 90.
    Tran, Dung-Trung
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Svensson, Gunnar
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Atomistic computation of the finite size effect in pair distribution function of nanoparticlesManuscript (preprint) (Other academic)
  • 91.
    Tran, Dung-Trung
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Svensson, Gunnar
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    TEM-based total scattering method for studying disorder of nanoparticles2014Conference paper (Other academic)
  • 92.
    Trushkina, Yulia
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Salazar-Alvarez, German
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Fabrication of Maghemite Nanoparticles with High Surface Area2019In: Nanomaterials, ISSN 2079-4991, Vol. 9, no 7, article id 1004Article in journal (Refereed)
    Abstract [en]

    Maghemite nanoparticles with high surface area were obtained from the dehydroxylation of lepidocrocite prismatic nanoparticles. The synthesis pathway from the precursor to the porous maghemite nanoparticles is inexpensive, simple and gives high surface area values for both lepidocrocite and maghemite. The obtained maghemite nanoparticles contained intraparticle and interparticle pores with a surface area ca. 30 x 10(3) m(2)/mol, with pore volumes in the order of 70 cm(3)/mol. Both the surface area and pore volume depended on the heating rate and annealing temperature, with the highest value near the transformation temperature (180-250 degrees C). Following the transformation, in situ X-ray diffraction (XRD) allowed us to observe the temporal decoupling of the decomposition of lepidocrocite and the growth of maghemite. The combination of high-angle annular dark-field imaging using scanning transmission electron microscopy (HAADF-STEM) and surface adsorption isotherms is a powerful approach for the characterization of nanomaterials with high surface area and porosity.

  • 93. Valvo, Mario
    et al.
    Liivat, Anti
    Eriksson, Henrik
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Edström, Kristina
    Iron-Based Electrodes Meet Water-Based Preparation, Fluorine-Free Electrolyte and Binder: A Chance for More Sustainable Lithium-Ion Batteries?2017In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 10, no 11, p. 2431-2448Article in journal (Refereed)
    Abstract [en]

    Environmentally friendly and cost-effective Li-ion cells are fabricated with abundant, non-toxic LiFePO4 cathodes and iron oxide anodes. A water-soluble alginate binder is used to coat both electrodes to reduce the environmental footprint. The critical reactivity of LiPF6-based electrolytes toward possible traces of H2O in water-processed electrodes is overcome by using a lithium bis(oxalato) borate (LiBOB) salt. The absence of fluorine in the electrolyte and binder is a cornerstone for improved cell chemistry and results in stable battery operation. A dedicated approach to exploit conversion-type anodes more effectively is also disclosed. The issue of large voltage hysteresis upon conversion/de-conversion is circumvented by operating iron oxide in a deeply lithiated Fe/Li2O form. Li-ion cells with energy efficiencies of up to 92% are demonstrated if LiFePO4 is cycled versus such anodes prepared through a prelithiation procedure. These cells show an average energy efficiency of approximately 90.66% and a mean Coulombic efficiency of approximately 99.65% over 320 cycles at current densities of 0.1, 0.2 and 0.3 mAcm(-2). They retain nearly 100% of their initial discharge capacity and provide an unmatched operation potential of approximately 2.85 V for this combination of active materials. No occurrence of Li plating was detected in three-electrode cells at charging rates of approximately 5C. Excellent rate capabilities of up to approximately 30C are achieved thanks to the exploitation of size effects from the small Fe nanoparticles and their reactive boundaries.

  • 94. Valvo, Mario
    et al.
    Philippe, Bertrand
    Lindgren, Fredrik
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Edström, Kristina
    Insight into the processes controlling the electrochemical reactions of nanostructured iron oxide electrodes in Li- and Na-half cells2016In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 194, p. 74-83Article in journal (Refereed)
    Abstract [en]

    The kinetics and the processes governing the electrochemical reactions of various types of iron oxide nanostructures (i.e., nanopowders, nanowires and thin-films) have been studied via cyclic voltammetry in parallel with Li- and Na-half cells containing analogous electrolytes (Li+/Na+, ClO4- in EC:DEC). The particular features arising from each electrode architecture are discussed and compared to shed light on the associated behaviour of the reacting nanostructured active materials. The influence of their characteristic structure, texture and electrical wiring on the overall conversion reaction upon their respective lithiation and sodiation has been analyzed carefully. The limiting factors existing for this reaction upon uptake of Li+ and Na+ ions are highlighted and the related issues in both systems are addressed. The results of this investigation clearly prove that the conversion of iron oxide into metallic Fe and Na2O is severely impeded compared to its analogous process upon lithiation, independently of the type of nanostructure involved in such reaction. The diffusion mechanisms of the different ions (i.e., Li+ vs. Na+) through the phases formed upon conversion, as well as the influence of various interfaces on the resulting reaction, appear to pose further constraints on an efficient use of these compounds.

  • 95.
    Verho, Oscar
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Gustafson, Karl P. J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nagendiran, Anuja
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bäckvall, Jan-Erling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mild and Selective Hydrogenation of Nitro Compounds using Palladium Nanoparticles Supported on Amino-Functionalized Mesocellular Foam2014In: ChemCatChem, ISSN 1867-3880, E-ISSN 1867-3899, Vol. 6, no 11, p. 3153-3159Article in journal (Refereed)
    Abstract [en]

    We present the utilization of a heterogeneous catalyst comprised of Pd nanoparticles supported on aminopropyl-functionalized siliceous mesocellular foam (Pd-0-AmP-MCF) for the selective hydrogenation of aromatic, aliphatic, and heterocyclic nitro compounds to the corresponding amines. In general, the catalytic protocol exclusively affords the desired amine products in excellent yields within short reaction times with the reactions performed at room temperature under ambient pressure of H-2. Moreover, the reported Pd nanocatalyst displayed excellent structural integrity for this transformation as it could be recycled multiple times without any observable loss of activity or leaching of metal. In addition, the Pd nanocatalyst could be easily integrated into a continuous-flow device and used for the hydrogenation of 4-nitroanisole on a 2.5 g scale, where the product p-anisidine was obtained in 95% yield within 2 h with a Pd content of less than 1 ppm.

  • 96.
    Verho, Oscar
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kärkäs, Markus
    Åkermark, Torbjörn
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Gustafson, Karl
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Svengren, Henrik
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Bäckvall, Jan-Erling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Well-Defined Palladium Nanoparticles Supported on Amino-Functionalized Siliceous Mesocellular Foam: An Efficient Heterogeneous Catalyst for Chemically-Induced H2O OxidationManuscript (preprint) (Other academic)
  • 97.
    Verho, Oscar
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nagendiran, Anuja
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Tai, Cheuk-wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nanopalladium on Amino-Functionalized Mesocellular Foam: An Efficient Catalyst for Suzuki Reactions and Transfer Hydrogenations2013In: ChemCatChem, ISSN 1867-3880, E-ISSN 1867-3899, Vol. 5, no 2, p. 612-618Article in journal (Refereed)
    Abstract [en]

    The applications of a heterogeneous Pd0-AmP-MCF nanoparticle catalyst in Suzuki cross-coupling reactions and transfer hydrogenations of alkenes are described. The catalyst was highly efficient for both transformations, resulting in 1)coupling of a wide range of aryl halides with various boronic acids in high yields and 2)chemoselective reduction of a variety of alkenes with the use of 1-methyl-1,4-cyclohexadiene as hydrogen donor. Moreover, the catalyst can be recycled several times without any significant decrease in activity or leaching of metal into solution, making the protocol economical and environmentally friendly. In the case of the Suzuki cross-coupling, a 15-fold increase in reaction rate was observed if the reaction was performed under microwave irradiation compared to conventional heating in an oil bath.

  • 98.
    Verho, Oscar
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nagendiran, Anuja
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nanopalladium on Amino-Functionalized Mesocellular Foam as an Efficient and Recyclable Catalyst for the Selective Transfer Hydrogenation of Nitroarenes to Anilines2014In: ChemCatChem, ISSN 1867-3880, E-ISSN 1867-3899, Vol. 6, no 1, p. 205-211Article in journal (Refereed)
    Abstract [en]

    Herein, we report on the use of nanopalladium on amino-functionalized siliceous mesocellular foam as an efficient heterogeneous catalyst for the transfer hydrogenation of nitroarenes to anilines. In all cases, the protocol proved to be highly selective and favored the formation of the desired aniline as the single product in high yields with short reaction times if naturally occurring and renewable -terpinene was employed as the hydrogen donor. Furthermore, the catalyst displayed excellent recyclability over five cycles and negligible leaching of metal into solution, which makes it an eco-friendly and economic catalyst to perform this transformation. The scalability of the protocol was demonstrated with the reduction of 4-nitroanisole on a 2g scale, in which p-anisidine was isolated in 98% yield.

  • 99.
    Verho, Oscar
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Torbjörn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Gustafson, Karl P. J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Svengren, Henrik
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Well-Defined Palladium Nanoparticles Supported on Siliceous Mesocellular Foam as Heterogeneous Catalysts for the Oxidation of Water2015In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 21, no 15, p. 5909-5915Article in journal (Refereed)
    Abstract [en]

    Herein, we describe the use of Pd nanoparticles immobilized on an amino-functionalized siliceous mesocellular foam for the catalytic oxidation of H2O. The Pd nanocatalyst proved to be capable of mediating the four-electron oxidation of H2O to O-2, both chemically and photochemically. The Pd nanocatalyst is easy to prepare and shows high chemical stability, low leaching, and recyclability. Together with its promising catalytic activity, these features make the Pd nanocatalyst of potential interest for future sustainable solar-fuel production.

  • 100.
    Volkov, Alexey
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Gustafson, Karl P. J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Verho, Oscar
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Adolfsson, Hans
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mild Deoxygenation of Aromatic Ketones and Aldehydes over Pd/C Using Polymethylhydrosiloxane as the Reducing Agent2015In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 54, no 17, p. 5122-5126Article in journal (Refereed)
    Abstract [en]

    Herein, a practical and mild method for the deoxygenation of a wide range of benzylic aldehydes and ketones is described, which utilizes heterogeneous Pd/C as the catalyst together with the green hydride source, polymethylhydrosiloxane. The developed catalytic protocol is scalable and robust, as exemplified by the deoxygenation of ethyl vanillin, which was performed on a 30 mmol scale in an open-to-air setup using only 0.085 mol% Pd/C catalyst to furnish the corresponding deoxygenated product in 93% yield within 3 hours at room temperature. Furthermore, the Pd/C catalyst was shown to be recyclable up to 6 times without any observable decrease in efficiency and it exhibited low metal leaching under the reaction conditions.

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