The electro-reduction of CO₂ presents an attractive method for storing intermittent renewable electricity as energy dense fuels. Polycrystalline Cu surfaces are unique for catalyzing the conversion of CO₂ to higher-order C1 and C2 fuels, including methane and ethylene, with moderate efficiencies. However, the long-lasting challenge has been attaining higher selectivity for desired products. The rational design of more selective and efficient catalysts requires mechanistic understanding of how Cu catalyzes the multi-proton and multi-electron conversion of CO₂.

In this talk, the origin of the unique catalytic activity and selectivity of Cu on CO₂ reduction reaction (CORR) is explored by tracking the surface intermediates using surface-enhanced FTIR (SEIRAS) and ambient-pressure XPS (APXPS), as well as density functional theory (DFT) calculations. Using this combined experimental and theoretical approach, we propose that not only M-C binding energy but also M-O binding energy plays a critical role in determining product selectivity for CORR. Key reaction intermediates on the surface as a function of potential have been identified and reaction mechanisms for the formation of experimentally detected reduced products have been proposed. Based on this new understanding, a strategy for rational electro-catalyst design for CORR that targets both activity and selectivity will be discussed. Perspectives for further optimization of the energetics of key reaction intermediates by tuning new knobs such as the interaction between intermediates and cations/anions in the electrolyte will also be considered.