Electrochemical Reduction of Carbon Dioxide to Syngas and Formate at Dendritic Copper–Indium Electrocatalysts

The ability to maintain high efficiencies while simultaneously tuning the selectivity of the electrochemical reduction of CO2 (ERC) using low-cost electrodes has proven to be one of the greatest obstacles to the widespread commercialization of this technology. In this study, we electrodeposit dendritic copper–indium alloys of various compositions and investigate their catalytic activity toward the reduction of CO2. These electrocatalysts are increasingly dendritic with higher In fraction and, depending on composition, consist of mixed phases of Cu, In, and Cu–In intermetallic phases. ERC at these electrodes produces formate at high efficiencies (up to 62% with a 80 at% In alloy, −1 V) while also tuning the CO/H2 ratio to achieve an ideal syngas composition with a 40 at% In alloy (−1 V). The observed product distribution as a function of alloy composition and applied potential is rationalized in terms of the relative adsorption strengths of CO and COOH intermediates at Cu and In sites and the distinct variation with applied potential induced by the differences in electronic structure. This study highlights the opportunities of using alloys to enhance control over the product distribution and suggests that suitable alloys could be promising catalysts for the inexpensive and efficient production of fuels.