The promise of using solar energy to promote the electrochemical reduction of CO2 to transportation fuels has motivated the research aimed at identifying highly active and selective catalysts that can achieve high current densities at low overpotentials, high catalyst selectivity for the reduction of CO2 to products other than CO, and low catalyst selectivity for the evolution of H2. Since Cu is the only metal known to produce significant quantities of hydrocarbons (e.g., CH4 and C2H4) and oxygenates (e.g., HCOOH, C2H5OH) we have focused on our efforts on maximizing the formation of these products and, in particular, C2H4 and C2H5OH. We have found that high yields of C2 vs C1 products can be achieved by electrochemical restructuring of polycrystalline Cu to enhance the formation of Cu(100) surface and by the use of CsHCO3 as the electrolyte. Theoretical analysis has revealed that Cu(100) surfaces are are particularly effective for forming C-C bonds via the coupling of adsorbed CO or CO and HCO species. The role of using Cs+ cation, rather than Na+ or K+ cations, in the electrolyte is ascribed to the lower pH at the cathode surface, particularly as overpotential is raised, which results in a higher local concentration of dissolved CO2. Further enhancement in the formation of C2 products is achieved by creating Cu bimetallic catalyst containing nano islands of Cu in a background of a metal that exhibits a high selectivity for CO2 reduction to CO. This talk will illustrate how it is possible to design electrocatalysts that exhibit faradaic efficiencies of 60% for C2 products, 30% for C1 products, and only 10% for H2.

Design of catalysts for the selective electrochemical reduction of CO2 to C2 hydrocarbons and oxygenates

251st National Meeting (2016)

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