Electrolyte Driven Highly Selective CO₂ Electroreduction at Low Overpotentials

Electrochemical CO₂ reduction reaction (CO₂RR) is a promising technology to use renewable electricity to convert CO₂ into value-added carbon-based products. The low-cost, active, selective, and stable catalysts will play a key role in achieving industrialized CO₂RR. The electrolyte assists a catalyst in achieving all its latent capability. Here the concentration effect of KHCO₃ in CO₂RR was systematically investigated on the low-cost core–shell structured Cu₂O@SnO_x nanoparticle-derived hybrid catalyst. An HCO₃^–-involved proton-coupled electron transfer was confirmed as the rate-determining step for CO₂RR on the hybrid catalyst in aqueous KHCO₃ solution based on the analysis of the reaction order and Tafel slope. The nearly 100% selectivity for CO was achieved in a highly concentrated KHCO₃ solution accompanied by a high cathodic energetic efficiency of 71.8%. It was attributed to the combined concentration effect of KHCO₃ with the related pH effect.