Vitamin B12 on Graphene for Highly Efficient CO2 Electroreduction.

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.