Synthesis of Low-Cost CuSn Catalysts for the Electrochemical Conversion of CO2 and Water to Formate and Syngas

The electrochemical reduction of CO2 offers a sustainable approach to transforming carbon dioxide into value-added products when powered by renewable energy. However, current electrocatalysts lack efficiency and selectivity, hindering commercial application. Combining tin’s high formate selectivity with copper’s ability to reduce CO2 via COOH* pathway offers a promising strategy. This synergy mitigates copper’s low selectivity, providing a cost-effective catalyst with enhanced performance over pure Sn-based systems. This work investigates CuSn bimetallic electrocatalysts synthesised by scalable electrodeposition onto gas diffusion layers to boost formate production. Catalytic performance and cell potential were evaluated at current densities ranging from 50 to 200 mA cm−2 and varying Sn compositions. Catalysts with Sn content below 4% predominantly formed CO and H2, but smaller particles and improved metal dispersion increased formate production. A catalyst containing 12% Sn achieved a maximum faradaic efficiency (FE) of 52% at 50 mA cm−2 with an iR-corrected potential of −0.56 V vs. SHE. At 200 mA cm−2, it exhibited a 30% FE for formate, along with 31% FE for CO and 9.3% FE for H2, while other gases contributed to less than 4% FE, indicating potential as syngas feedstock. Higher Sn content, combined with smaller, well-distributed particles, effectively suppressed H2, CO, and other by-products, highlighting a strong dependence of FE on Sn content and bimetallic distribution, demonstrating compositional tuning importance via electrodeposition.