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1.
Chem Commun (Camb) ; 58(14): 2323-2326, 2022 Feb 15.
Article in English | MEDLINE | ID: mdl-35076040

ABSTRACT

Replacing Pt-based catalysts with cost-effective, highly efficient, and durable platinum group metal-free catalysts for the oxygen reduction reaction (ORR) is crucial for commercializing hydrogen fuel cells. Herein, we present a highly active Fe-N-C electrocatalyst that contains both Fe nanoparticles and FeNx active sites derived from an Fe-doped carbonized zeolitic imidazolate framework (ZIF-8). It is found that adjusting the doping amount of Fe in the Fe-doped ZIF-8 precursor alters the morphology of the catalyst after heat treatment. The Fe-N-C-300 composite catalyst with the optimized Fe doping amount exhibits excellent activity, good stability, and remarkable methanol tolerance in the challenging acid environment. This study reveals that a suitable amount of Fe nanoparticles in the catalyst can alter the structure of the FeNx active moieties and increase three-phase boundaries to boost the mass transport, thus leading to improved fuel cell performance. This will have implications for using Fe-N-C catalysts in real applications, as the formation of Fe NPs during the synthesis and reaction is almost inevitable.

2.
ACS Appl Mater Interfaces ; 12(37): 41288-41293, 2020 Sep 16.
Article in English | MEDLINE | ID: mdl-32809795

ABSTRACT

Combining the advantages of homogeneous and heterogeneous catalytic systems has emerged as a promising strategy for electrochemical CO2 reduction although developing robust, active, product-selective, and easily available, catalysts remains a major challenge. Herein, we report the electroreduction of CO2 catalyzed by cobalt and benzimidazole containing Vitamin B12 immobilized on the surface of reduced graphene oxide (rGO). This hybrid system with a naturally abundant molecular catalyst produces CO with high selectivity and a constant current density in an aqueous buffer solution (pH 7.2) for over 10 h. A Faradaic efficiency (FE) of 94.5% was obtained for converting CO2 to CO at an overpotential of 690 mV with a CO partial current density (jCO) of 6.24 mA cm-2 and a turnover frequency (TOF) of up to 28.6 s-1. A higher jCO (13.6 mA cm-2) and TOF (52.4 s-1) can be achieved with this system at a higher overpotential (790 mV) without affecting the product selectivity (∼94%) for CO formation. Our experimental findings are corroborated with density functional theory (DFT) studies to understand the influence of the covalently attached and redox-active benzimidazole unit. To the best of our knowledge, this is the first example of naturally abundant vitamin being immobilized on a conductive surface for highly efficient CO2 electroreduction.


Subject(s)
Carbon Dioxide/chemistry , Graphite/chemistry , Vitamin B 12/chemistry , Density Functional Theory , Electrochemical Techniques , Hydrogen-Ion Concentration , Oxidation-Reduction , Particle Size , Surface Properties
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