Electrochemical CO₂ Reduction on Gas Diffusion Electrodes: Enhanced Selectivity of In–Bi Bimetallic Particles and Catalyst Layer Optimization through a Design of Experiment Approach

CO2 electroreduction to formate powered by renewable energy is an attractive strategy to recycle carbon. Electrode materials showing high selectivity for formate at high current densities are post-transition metals such as Sn, In, Pb, Hg, and Bi. Scaling up the CO2 electroreduction technology to industrial size will require, among other things, maximization of selectivity at high current densities. We show here that InBi electrocatalysts provide enhanced selectivity compared to pure In and Bi and that a proper formulation of the catalyst layer can have a profound impact on the performance of gas diffusion electrode electrolyzers. The best performing electrodes screened in this study show nearly 100% current efficiency at current densities up to 400 mA cm–2 for 2 h. Additionally, one electrode was shown to operate at a current density of 200 mA cm–2 for 48 h at a current efficiency of 85% and remained operating with a current efficiency above 50% for 124 h.