Electroreduction of Carbon Dioxide to Hydrocarbons Using Bimetallic Cu-Pd Catalysts with Different Mixing Patterns

Electrochemical conversion of CO2 holds promise for utilization of CO2 as a carbon feedstock and for storage of intermittent renewable energy. Presently Cu is the only metallic electrocatalyst known to reduce CO2 to appreciable amounts of hydrocarbons, but often a wide range of products such as CO2 HCOO-, and H-2 are formed as well. Better catalysts that exhibit high activity and especially high selectivity for specific products are needed. Here a range of bimetallic Cu-Pd catalysts with ordered, disordered, and phase-separated atomic arrangements (Cu-at:Pd-at = 1:1), as well as two additional disordered arrangements (Cu3Pd and CuPd3 with Cu-at:Pd-at = 3:1 and 1:3), are studied to determine key factors needed to achieve high selectivity for C1 or C2 chemicals in CO2 reduction. When compared with the disordered and phase-separated CuPd catalysts, the ordered CuPd catalyst exhibits the highest selectivity for Cl products (>80%). The phase-separated CuPd and Cu3Pd achieve higher selectivity (>60%) for C2 chemicals than CuPd3 and ordered CuPd, which suggests that the probability of dimerization of Cl intermediates is higher on surfaces with neighboring Cu atoms. Based on surface valence band spectra, geometric effects rather than electronic effects seem to be key in determining the selectivity of bimetallic Cu Pd catalysts. These results imply that selectivities to different products can be tuned by geometric arrangements. This insight may benefit the design of catalytic surfaces that further improve activity and selectivity for CO2 reduction.