Exploring Mg-Sn alloys as electrocatalysts for CO2 electroreduction

Abstract

Tin is one of the most selective electrocatalysts for CO2 reduction (CO2RR), mostly thanks to its poor activity towards the hydrogen evolution reaction (HER). Still, Sn electrodes are limited by their very high overpotential. We decided to investigate the electrochemical CO2RR catalytic activity of tin-magnesium alloys that can be easily obtained by thermal annealing from the elemental metallic powders. We found that the alloys exhibit a slightly improved activity and selectivity towards CO2RR with formate as dominant product according to electrochemical and chemical analysis. Post-mortem characterization confirmed that this effect is not due to the alloys performance, but to Sn re-structuration. Most of the Mg is leached from the alloy into the electrolyte during CO2RR, leaving a highly porous Sn structure. These changes in morphology and surface area as triggered by Mg leaching, appear to be at the origin of the enhanced electrocatalytic performance.