Activity and Selectivity in the Electrochemical Reduction of CO2 at CuSnx Electrocatalysts Using a Zero-Gap Membrane Electrode Assembly

In this study Cu, Sn, and bimetallic CuSn_x nanoparticles were synthesized and evaluated as electrocatalysts for CO₂ reduction using zero gap membrane electrode assemblies. Results show bimetallic electrocatalysts with Sn contents above 10% yield formate as a primary product with Faradaic Efficiencies near 70% at 350 mA cm⁻². Cu-Sn_x electrocatalysts with less than 10% Sn yield CO at current densities below 350 mA cm⁻² and relatively lower cell potentials. When the low-Sn content bimetallic electrocatalysts were evaluated in alkaline anolytes at 350 mA cm⁻², ethanol was recorded as the primary product (FE = 48.5% at E_cell ≥ 3.0 V). We propose enhanced C₂ activity and selectivity originate from Cu dimers adjacent to Sn atoms for bimetallic electrocatalyst with low-Sn content. The C₂ active sites are lost when the surface Sn content exceeds 25%–38%.