4 research outputs found

    Enhanced Direct Electron Transfer Mediated Contaminant Degradation by Fe(IV) Using a Carbon Black-Supported Fe(III)-TAML Suspension Electrode System

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    Iron complexes of tetra-amido macrocyclic ligands (Fe-TAML) are recognized to be effective catalysts for the degradation of a wide range of organic contaminants in homogeneous conditions with the high valent Fe(IV) and Fe(V) species generated on activation of the Fe-TAML complex by hydrogen peroxide (H2O2) recognized to be powerful oxidants. Electrochemical activation of Fe-TAML would appear an attractive alternative to H2O2 activation, especially if the Fe-TAML complex could be attached to the anode, as this would enable formation of high valent iron species at the anode and, importantly, retention of the valuable Fe-TAML complex within the reaction system. In this work, we affix Fe-TAML to the surface of carbon black particles and apply this “suspension anode” process to oxidize selected target compounds via generation of high valent iron species. We show that the overpotential for Fe(IV) formation is 0.17 V lower than the potential required to generate Fe(IV) electrochemically in homogeneous solution and also show that the stability of the Fe(IV) species is enhanced considerably compared to the homogeneous Fe-TAML case. Application of the carbon black-supported Fe-TAML suspension anode reactor to degradation of oxalate and hydroquinone with an initial pH value of 3 resulted in oxidation rate constants that were up to three times higher than could be achieved by anodic oxidation in the absence of Fe-TAML and at energy consumptions per order of removal substantially lower than could be achieved by alternate technologies

    Built-in Electric Field-Induced Work Function Reduction in C–Co<sub>3</sub>O<sub>4</sub> for Efficient Electrochemical Nitrogen Reduction

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    Co3O4 is a highly selective catalyst for the electrochemical conversion of N2 to NH3. However, the large work function (WF) of Co3O4 leads to unsatisfactory activity. To address this issue, a strong built-in electric field (BIEF) was constructed in Co3O4 by doping C atoms (C–Co3O4) to reduce the WF for improving the electrocatalytic performance. C–Co3O4 exhibited a remarkable NH3 yield of 38.5 μg h–1 mgcat–1 and a promoted FE of 15.1% at −0.3 V vs RHE, which were 2.2 and 1.9 times higher than those of pure Co3O4, respectively. Kelvin probe force microscopy (KPFM), zeta potential, and ultraviolet photoelectron spectrometry (UPS) confirmed the formation of strong BIEF and WF reduction in C–Co3O4. Additionally, in situ Raman measurements and density functional theory (DFT) calculations revealed the relationship between BIEF and WF and provided insights into the reaction mechanism. Our work offers valuable guidance for the design and development of more efficient nitrogen reduction catalysts

    Deciphering the Stability Mechanism of Cu Active Sites in CO<sub>2</sub> Electroreduction via Suppression of Antibonding Orbital Occupancy in the O 2p-Cu 3d Hybridization

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    Copper-based catalysts, hallmarked by their ideal C–C coupling energy facilitated by the symbiotic presence of Cu+ and Cu0 active sites, are poised to revolutionize the selective electrochemical reduction of CO2 to C2H4. Regrettably, these catalysts are beleaguered by the unavoidable diminution of Cu+ to Cu0 during the reaction process, resulting in suboptimal C2H4 yields. To circumvent this limitation, we have judiciously mitigated the antibonding orbital occupancy in the O 2p and Cu+ 3d hybridization by introducing Cu defects into Cu2O, thereby augmenting the Cu–O bond strength to stabilize Cu+ sites and further decipher the stabilization mechanism of Cu+. This structural refinement, illuminated by meticulous DFT calculations, fosters a heightened free energy threshold for the hydrogen evolution reaction (HER), while orchestrating a thermodynamically favorable milieu for enhanced C–C coupling within the Cu-deficient Cu2O (Cuv-Cu2O). Empirically, Cuv-Cu2O has outperformed its pure Cu2O counterpart, exhibiting a prominent C2H4/CO ratio of 1.69 as opposed to 1.01, without conceding significant ground in C2H4 production over an 8 h span at −1.3 V vs RHE. This endeavor not only delineates the critical influence of antibonding orbital occupancy on bond strength and reveals the deep mechanism about Cu+ sites but also charts a pioneering pathway in the realm of advanced materials design

    Cu-Modified Palladium Catalysts: Boosting Formate Electrooxidation via Interfacially OH<sub>ad</sub>-Driven H<sub>ad</sub> Removal

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    Direct formate fuel cells have gained traction due to their eco-friendly credentials and inherent safety. However, their potential is hampered by the kinetic challenges of the formate oxidation reaction (FOR) on Pd-based catalysts, chiefly due to the unfavorable adsorption of hydrogen species (Had). These species clog the active sites, hindering efficient catalysis. Here, we introduce a straightforward strategy to remedy this bottleneck by incorporating Pd with Cu to expedite the removal of Pd–Had in alkaline media. Notably, Cu plays a pivotal role in bolstering the concentration of hydroxyl adsorbates (OHad) on the surface of catalyst. These OHad species can react with Had, effectively unblocking the active sites for FOR. The as-synthesized catalyst of PdCu/C exhibits a superior FOR performance, boasting a remarkable mass activity of 3.62 A mg–1. Through CO-stripping voltammetry, we discern that the presence of Cu in Pd markedly speeds up the formation of adsorbed hydroxyl species (OHad) at diminished potentials. This, in turn, aids the oxidative removal of Pd–Had, leveraging a synergistic mechanism during FOR. Density functional theory computations further reveal intensified interactions between adsorbed oxygen species and intermediates, underscoring that the Cu–Pd interface exhibits greater oxyphilicity compared to pristine Pd. In this study, we present both experimental and theoretical corroborations, unequivocally highlighting that the integrated copper species markedly amplify the generation of OHad, ensuring efficient removal of Had. This work paves the way, shedding light on the strategic design of high-performing FOR catalysts
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