Understanding the structure of Ru(V)-oxo species is crucial for designing novel catalysts for sustainable energy applications, such as water splitting for green hydrogen production. This study reports the EPR detection of a Ru(V)-oxo intermediate stabilized by terpyridine and phenanthroline carboxylate ligands. The interaction between the carboxylate group and the ruthenium center, along with PCET-dependent hemilability under oxidative conditions, plays a critical role in achieving the high-valent state. Subtle changes in the coordination environment around the central metal also proved to be essential. Low-temperature NMR, high-resolution mass spectrometry, UV–Vis spectroscopy, and density functional theory calculations support these findings.

A series of homoleptic ruthenium(II)-bis(pincer) complexes (Ru1-4) featuring unsymmetrical CNN pincer ligands are synthesized and characterized using spectroscopic and single-crystal X-ray diffraction techniques. Investigation of these complexes for catalytic electrochemical water oxidation reveals complexes Ru1 and Ru3, with proton-responsive protic-NHC ligands having β-NH functionalities, demonstrate better water oxidation performance compared to their classical-NHC counterparts, Ru2 and Ru4, respectively. Cyclic voltammetry at low temperatures (−30 °C) was conducted to gain insights into the potential active intermediates. The foot of the wave analysis (FOWA) was used to elucidate the operating reaction mechanism, revealing a water nucleophilic attack (WNA) mechanism. Catalytic Tafel plots are employed to evaluate the performance and for benchmarking the catalyst. The Ru1 complex is found to be the most efficient catalyst, among all four complexes in this study, at a modest overpotential (̴ 330 mV vs NHE) with an impressive TON value of 1.6 × 10⁵ over a period of 8 h, giving TOF of 5.53 s⁻¹. Even at a lower overpotential of 140 mV vs NHE, the TON (62560) for Ru1 outperforms most of the homogeneous Ru-systems, other than the Ru(bda) family of complexes, reported so far for the electrochemical water oxidation.

Chlorinated volatile organic compounds (Cl-VOCs), used in dry cleaning and textiles are stable and resistant to degradation, posing significant environmental challenges. This has led to a growing focus on developing effective treatment technologies for wastewater and groundwater contamination. This study demonstrates the efficacy of cationic analogues of vitamin B₁₂ (VB₁₂) as swift electron transfer mediators for the reduction of perchloroethylene (PCE), trichloroethene (TCE), and dichloromethane (DCM) in a homogeneous aqueous solution using Ti^III citrate as the primary electron donor. By utilizing cobalt tetratrimethylammonium phthalocyanine (CoTTMeAPc) for the first time in dechlorination process, notable degradation efficiencies were achieved. Within 5 min, CoTTMeAPc achieved high degradation efficiencies (94.6 % for PCE, 91.6 % for TCE, and 55.4 % for DCM), outperforming VB₁₂ (21.6 %, 15.4 %, and 6.7 %, respectively) within the same period, as well as insoluble CoPc, which degraded only 27.4 %, 46.7 %, and 21.9 % within 20 min. This result highlights a novel application of CoTTMeAPc in dechlorination, demonstrating its potential for rapid and effective pollutant removal. The effects of various concentrations of the initial chlorinated compound, catalyst, and reductant concentrations, as well as pH, were investigated in the dechlorination reaction. The reaction was monitored through UV/VIS spectroscopy to unravel the reason behind the substantial degradation of chlorinated compounds using reduced CoTTMeAPc. The plausible mechanism is proposed by the analysis of intermediate products generated at different time intervals during this study, UV-Vis spectral analysis and supported by the previously published reports. This study provides new insights into the degradation of halogenated compounds utilizing water-soluble cationic cobalt phthalocyanine complexes. While this research focuses on chemical degradation, the findings are expected to create opportunities for future exploration in bioremediation, potentially involving microorganisms.

Efficient production of hydrogen via water electrolysis is one of the promising approaches to enable a complete fossil-free energy transition. Hydrogen can be utilized alongside renewable energy sources like wind and solar to smooth out their power production. It can also serve as a standalone solution to stabilize electrical grids and support various industrial processes. The most promising electrolyzer to be used for grid applications and alongside renewable energy sources is a proton exchange membrane electrolyzer, due to its fast dynamics. Due to their high cost and relatively short lifetime, they are not widely used in electric grids or industry today. With particularly designed electrodes, the proton exchange membrane electrolyzers can operate under cyclic polarity switching, which makes the electrodes self-regenerate. This increases the lifetime of the proton exchange membrane electrolyzers, as well as minimizes their efficiency drop over time. In order for polarity switching to be implemented on an industrial level, a novel solution to ensure that the hydrogen always goes to the right storage unit and is kept ultra-pure is of great importance. This paper presents an innovative modular gas routing system that enables safe polarity switching and prevents cross-contamination of gases through automatic valve control and a self-cleaning mechanism. The system was also implemented in a proof-of-concept prototype.

Conversion of carbon dioxide (CO₂) into value-added products is aimed to develop scalable technologies to promote a circular economy. While the electrochemical reduction of CO₂ to carbon monoxide (CO) and formic acid has advanced significantly, a major challenge remains achieving further reduced and more energy-dense products, such as methanol (MeOH), through sustainable pathways. Herein, we report a molecular electrode capable of direct six-electron reduction of CO₂ to MeOH using water as a proton source with a global Faradaic efficiency (FE_G) of 22% and product selectivity of 61% for MeOH. The design consists of an active copper-hydride center surrounded by two closely spaced benzimidazole–hydride units, facilitating the catalytic transfer of three hydrides to produce MeOH. The concurrent formation of formic acid and the absence of formaldehyde suggest that MeOH is generated via a formato pathway. DFT investigations revealed the complete mechanistic pathway, which supports the experimental observations. The morphology and stability of the electrode were evaluated before and after prolonged electrolysis (12 h) experiments using electron microscopic techniques.

Green hydrogen production from water is one attractive route to non-fossil fuel and a potential source of clean energy. Hydrogen is not only a zero-carbon energy source but can also be utilized as an efficient storage of electrical energy generated through various other sources, such as wind and solar. Cost-effective and environmentally benign direct hydrogen production through neutral water (∼pH 7) reduction is particularly challenging due to the low concentration of protons. There is currently a major need for easy-to-prepare, robust, as well as active electrode materials. Herein we report three new molecular electrodes that were prepared by anchoring commercially available, and environmentally benign cobalt-containing electrocatalysts with three different ligand frameworks (porphyrin, phthalocyanine, and corrin) on a structurally modified graphite foil surface. Under the studied reaction conditions (over 7 h at 22°C), the electrode with Co-porphyrin is the most efficient for the water reduction with starting ∼740 mV onset potential (OP) (vs. RHE, current density 2.5 mA/cm2) and a Tafel slope (TS) of 103 mV/dec. It is followed by the molecular electrodes having Co-phthalocyanine [825 mV (OP), 138 mV/dec (TS)] and Vitamin-B12 (Co-corrin moiety) [830 mV (OP), 194 mv/dec (TS)]. A clear time-dependent improvement (>200 mV over 3 h) in the H2 production overpotential with the Co-porphyrin-containing cathode was observed. This is attributed to the activation due to water coordination to the Co-center. A long-term chronopotentiometric stability test shows a steady production of hydrogen from all three cathode surfaces throughout seven hours, confirmed using an H2 needle sensor. At a current density of 10 mA/cm2, the Co-porphyrin-containing electrode showed a TOF value of 0.45 s−1 at 870 mV vs. RHE, whereas the Co-phthalocyanine and Vitamin-B12-containing electrodes showed 0.37 and 0.4 s−1 at 1.22 V and 1.15 V (vs. RHE), respectively.

Branched perfluorooctane sulfonic acid (PFOS) is recognized as a threatening environmental pollutant due to its high persistence and bioaccumulation in various environmental matrices as well as for its toxic effects on humans and wildlife even at very low concentrations. This study reports the first investigation of branched PFOS defluorination catalyzed by metal phthalocyanines. The reaction conditions were optimized using different reductants and temperatures. CobaltII phthalocyanine, when combined with TiIII citrate as a reducing agent, was able to defluorinate 10.9% of technical PFOS within 8 hours. In contrast, vitamin B12 only showed 2.4% defluorination during the same time period, under similar conditions. The defluorination mediated by the cobaltII phthalocyanine and TiIII citrate system corresponds to 54.5% of all branched PFOS isomers (br-PFOS isomers). Isomer-specific degradation was also investigated via high-resolution LC-orbitrap followed by their relative rates. The difference in catalytic efficacy of various phthalocyanine complexes is rationalized by their structures and electrochemical response. Lastly, a new defluorination mechanism is proposed based on the newly detected degradation products after the phthalocyanine treatment and previous studies. CobaltII phthalocyanine in the presence of TiIII citrate acts as an efficient reducing agent which was able to defluorinate 54.5% of all branched PFOS isomers.

Nano zero-valent metals (nZVMs) have been extensively utilized for decades in the reductive remediation of groundwater contaminated with chlorinated organic compounds, owing to their robust reducing capabilities, simple application, and cost-effectiveness. Nevertheless, there remains a dearth of information regarding the efficient reductive defluorination of linear or branched per- and polyfluoroalkyl substances (PFASs) using nZVMs as reductants, largely due to the absence of appropriate catalysts. In this work, various soluble porphyrin ligands [[meso‑tetra(4-carboxyphenyl)porphyrinato]cobalt(III)]Cl·7H2O (CoTCPP), [[meso‑tetra(4-sulfonatophenyl) porphyrinato]cobalt(III)]·9H2O (CoTPPS), and [[meso‑tetra(4-N-methylpyridyl) porphyrinato]cobalt(II)](I)4·4H2O (CoTMpyP) have been explored for defluorination of PFASs in the presence of the nZn0 as reductant. Among these, the cationic CoTMpyP showed best defluorination efficiencies for br-perfluorooctane sulfonate (PFOS) (94%), br-perfluorooctanoic acid (PFOA) (89%), and 3,7-Perfluorodecanoic acid (PFDA) (60%) after 1 day at 70 °C. The defluorination rate constant of this system (CoTMpyP-nZn0) is 88–164 times higher than the VB12-nZn0 system for the investigated br-PFASs. The CoTMpyP-nZn0 also performed effectively at room temperature (55% for br-PFOS, 55% for br-PFOA and 25% for 3,7-PFDA after 1day), demonstrating the great potential of in-situ application. The effect of various solubilizing substituents, electron transfer flow and corresponding PFASs defluorination pathways in the CoTMpyP-nZn0 system were investigated by both experiments and density functional theory (DFT) calculations. SYNOPSIS: Due to the unavailability of active catalysts, available information on reductive remediation of PFAS by zero-valent metals (ZVMs) is still inadequate. This study explores the effective defluorination of various branched PFASs using soluble porphyrin-ZVM systems and offers a systematic approach for designing the next generation of catalysts for PFAS remediation.

The production of pyocyanin by Pseudomonas aeruginosa increases its virulence, fitness and biofilm formation. Pyocyanin is also a redox molecule and we hypothesize that ascorbic acid being an antioxidant will interact with pyocyanin. The main objective of this study was to investigate the potential interaction of ascorbic acid with pyocyanin, and also to investigate the impact of ascorbic acid in combination with Furanone-30 on quorum sensing and biofilm formation of P. aeruginosa. When incubated with ascorbic acid, hyperchromic and hypsochromic shifts in pyocyanin absorbance peaks at 385 nm and 695 nm were observed. In the presence of dehydroascorbic acid and citric acid, these shifts were absent, indicating that the intrinsic antioxidant property of ascorbic acid was probably essential in binding to pyocyanin. NMR spectroscopy showed shifts in ¹H NMR pyocyanin peaks between 8.2 to 5.8 ppm when incubated in the presence of ascorbic acid. Density Functional Theory (DFT) supported potential interactions between the -CH₂OH or -OH moieties of ascorbic acid with the -C=O moiety of pyocyanin. The pyocyanin-ascorbic acid complex impaired pyocyanin binding to DNA. Ascorbic acid combined with furanone-30 elevated quorum-sensing inhibition in P. aeruginosa, which was directly associated with significantly reduced P. aeruginosa virulence, adhesion, aggregation and biofilm formation and enhanced antibiotic-mediated bacterial killing. This study demonstrated that the antioxidant ascorbic acid directly binds to pyocyanin, modulates its structure and results in disruption of biofilm formation and associated tolerance to antibiotics.

The instability of molecular electrodes under oxidative/reductive conditions and insufficient understanding of the metal oxide-based systems have slowed down the progress of H₂-based fuels. Efficient regeneration of the electrode's performance after prolonged use is another bottleneck of this research. This work represents the first example of a bifunctional and electrochemically regenerable molecular electrode which can be used for the unperturbed production of H₂ from water. Pyridyl linkers with flexible arms (–CH₂–CH₂–) on modified fluorine-doped carbon cloth (FCC) were used to anchor a highly active ruthenium electrocatalyst [Ru^II(mcbp)(H₂O)₂] (1) [mcbp²⁻ = 2,6-bis(1-methyl-4-(carboxylate)benzimidazol-2-yl)pyridine]. The pyridine unit of the linker replaces one of the water molecules of 1, which resulted in RuPFCC (ruthenium electrocatalyst anchored on –CH₂–CH₂–pyridine modified FCC), a high-performing electrode for oxygen evolution reaction [OER, overpotential of ∼215 mV] as well as hydrogen evolution reaction (HER, overpotential of ∼330 mV) at pH 7. A current density of ∼8 mA cm⁻² at 2.06 V (vs. RHE) and ∼−6 mA cm⁻² at −0.84 V (vs. RHE) with only 0.04 wt% loading of ruthenium was obtained. OER turnover of >7.4 × 10³ at 1.81 V in 48 h and HER turnover of >3.6 × 10³ at −0.79 V in 3 h were calculated. The activity of the OER anode after 48 h use could be electrochemically regenerated to ∼98% of its original activity while it serves as a HE cathode (evolving hydrogen) for 8 h. This electrode design can also be used for developing ultra-stable molecular electrodes with exciting electrochemical regeneration features, for other proton-dependent electrochemical processes.