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  • 1.
    Akhtar, Farid
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Liu, Qingling
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Strong and binder free structured zeolite sorbents with very high CO2-over-N-2 selectivities and high capacities to adsorb CO2 rapidly2012In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 5, no 6, p. 7664-7673Article in journal (Refereed)
    Abstract [en]

    Mechanically strong monoliths of zeolite NaKA with a hierarchy of pores displayed very high CO2-over-N-2 selectivity. The zeolite monoliths were produced by pulsed current processing (PCP) without the use of added binders and with a preserved microporous crystal structure. Adsorption isotherms of CO2 and N-2 were determined and used to predict the co-adsorption of CO2 and N-2 using ideal adsorbed solution theory (IAST). The IAST predictions showed that monolithic adsorbents of NaKA could reach an extraordinarily high CO2-over-N-2 selectivity in a binary mixture with a composition similar to flue gas (15 mol% CO2 and 85 mol% N2 at 25 degrees C and 101 kPa). Structured NaKA monoliths with a K+ content of 9.9 at% combined a CO2-over-N-2 selectivity of >1100 with a high CO2 adsorption capacity (4 mmol g(-1)) and a fast adsorption kinetics (on the order of one minute). Estimates of a figure of merit (F) based on IAST CO2-over-N-2 selectivity, and time-dependent CO2 uptake capacity, suggest that PCP-produced structured NaKA with a K+ content of 9.9 at% offers a performance far superior to 13X adsorbents, in particular at short cycle times.

  • 2.
    Cui, Daqing
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Low, Jeanett
    Spahiu, Kastriot
    Environmental behaviors of spent nuclear fuel and canister materials2011In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 4, no 7, p. 2537-2545Article in journal (Refereed)
    Abstract [en]

    The world's first spent nuclear fuel repository concept (Swedish KBS-3) is illustrated and the results of experiments on environmental behaviors of spent fuel and canister materials under a potential canister breaching at early stage of disposal are reported. In a deoxygenated synthetic groundwater (2 mM NaHCO(3)) under radiation (gamma 0.9 Gy h(-1)), inventory fraction leaching rates of fission-products ((137)Cs, (90)Sr and (99)Tc) and actinides ((238)U, (237)Np) from a spent fuel segment were found to be around 10(-6) and 10(-7) per day, respectively. A cast-iron canister surface was found to be able to immobilize (238)U, (90)Sr, (99)Tc and (237)Np dissolved from spent fuel, but a copper surface could not. In the presence of the oxidative species generated from water radiolysis, the corrosion rates of waste canister materials, copper and cast-iron were found to be 1 and 30 mm per year, respectively. The observation of insignificant dissolution of spent fuel in the leaching solution equilibrated with 0.1 atm H(2) is explained by the reducing effects of H(2) in the presence of fission-product alloy particles (Mo-Tc-Ru-Rh-Pd) as catalysts and dissolved Fe(II) in groundwater. The coating effect of ferric precipitates on spent nuclear fuel dissolution is also discussed.

  • 3. Datta, Shuvo Jit
    et al.
    Oleynikov, Peter
    Moon, Won Kyung
    Ma, Yanhang
    Mayoral, Alvaro
    Kim, Hyuncheol
    Dejoie, Catherine
    Song, Mee Kyung
    Terasaki, Osamu
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Shanghai Tech University, China.
    Yoon, Kyung Byung
    Removal of Sr-90 from highly Na+-rich liquid nuclear waste with a layered vanadosilicate2019In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 12, no 6, p. 1857-1865Article in journal (Refereed)
    Abstract [en]

    Capture of trace amounts (parts per trillion or ppt level) of Sr-90 from highly Na+-rich (5 M or 115 000 parts per million) liquid wastes produced from reprocessing of spent nuclear fuel rods is crucial for continuous operation of nuclear power plants. However, no sorbents have shown such abilities. We now report that a novel layered vanadosilicate, SGU-7, with the unit cell parameters of a = 23.58 A, b = 30.04 A, c = 12.31 A, b = 100.28, and space group of P12(1)/a1, can effectively capture Sr-90 from a 5 M Na+ solution containing 6.2 ppt of Sr-90. It also effectively captures 1-ppb level Ra-226 from 2 M NaCl solution, and Cs+ and Sr2+ from groundwater, demonstrating that it can be immediately used to remedy groundwater and soil contaminated with Ra-226, Sr-90, and Cs-137.

  • 4. 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.

  • 5. Tung, Cao
    et al.
    Docao, Son
    Hwang, In Chul
    Song, Mee Kyung
    Choi, Do Young
    Moon, Dohyun
    Oleynikov, Peter
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Yoon, Kyung Byung
    Capture of iodine and organic iodides using silica zeolites and the semiconductor behaviour of iodine in a silica zeolite2016In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 9, no 3, p. 1050-1062Article in journal (Refereed)
    Abstract [en]

    During the reprocessing of spent nuclear fuel rods, a highly moist off-gas mixture containing various volatile radioactive species, such as iodine (I-2), organic iodides and nitric acid, is produced. Efforts have been made to devise materials, which can effectively capture radioactive iodine (I-2) and organic iodides from the off-gas mixture without being damaged by moisture, nitric acid, and I-2. In the investigation described herein, we observed that all-silica zeolites, such as silicalite-1 and Si-BEA, are stable in 5 M nitric acid and adsorb I-2, CH3I, and CH3CH2I from highly acidic off-gas mixture to much greater extents than activated carbon does. In particular, the hydrophobicity-intensified silicalite-1 performs best. We further found that I-2 forms a unique semiconducting three-dimensional supramolecular network within the silicalite-1 channels. The conductivity of the fully I-2 loaded silicalite-1 is observed to be ca. 10(4) S m(-1), which is ca. 10(8)-fold higher than that of solid I-2.

  • 6. Zhong, Miao
    et al.
    Ma, Yanhang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Oleynikov, Peter
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Domen, Kazunari
    Delaunay, Jean-Jacques
    A conductive ZnO-ZnGaON nanowire-array-on-a film photoanode for stable and efficient sunlight water splitting2014In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 7, no 5, p. 1693-1699Article in journal (Refereed)
    Abstract [en]

    We report highly stable and efficient sunlight water splitting on a ZnO-ZnGaON nanowire-array-on-a-film photoanode without the assistance of any co-catalyst. The single crystalline ZnO-ZnGaON nanowirearray- on-a-film photoanode was synthesized via a high-temperature vapor-phase diffusion reaction of gallium (Ga) and nitrogen (N) on a single crystal domain ZnO nanowire-array-on-a-film structure. The synthesized ZnO-ZnGaON photoanode offers visible light absorption through N incorporation, improved electrical conductivity via Ga incorporation, and structural advantages with the high-aspect-ratio nanowire array. Compared to the chemically unstable ZnO nanowire photoanode, the ZnO-ZnGaON nanowire photoanode significantly improves the anti-photocorrosive ability for water splitting. A highly stable photocurrent density of similar to 1.5 mA cm(-2) is obtained with the ZnO-ZnGaON nanowire photoanode at an applied bias of 0.8 V-RHE under continuous sunlight illumination over five hours without noticeable degradation.

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