CO 2 Reduction on Liquid GaInSn‐Metal: Dynamics of the Electrode–Electrolyte Interface

Abstract Post‐transition liquid metal (LM) alloys are of increasing interest for the electro‐reduction of CO 2 . Besides avoiding coking effects, they often exhibit an electric field‐induced accumulation of elements at their interface, which can be used to tune catalytic activity and product selectivity. However, mechanistic insights into these systems remain sparse. In this study, we investigate the ternary GaInSn alloy in DMF‐based electrolyte. We demonstrate that even small amounts of water in DMF significantly increase the CO 2 reduction rate. Under optimized conditions (2 M water in DMF at −2.7 V versus Ag/Ag + ), the overall current density is approximately −3 mA/cm 2 , two orders of magnitude higher than in anhydrous electrolysis. The Faradaic efficiency for HCOOH and CO production is around 60% and 30%, respectively, whereas the competing hydrogen evolution remains a minor side product. Analysis of the electrolyte after CO 2 electrolysis reveals varying amounts of expelled tin and gallium. This suggest that an enrichment of the interface in tin may be responsible for the high selectivity toward HCOOH. Our study provides a better mechanistic understanding of CO 2 reduction on GaInSn and shows that the dynamic elemental composition should always be considered for the interpretation of experimental results.