In-situ oxidation of Sn catalysts for long-term electrochemical CO2 reduction to formate

Abstract

Electrochemical carbon dioxide (CO2) reduction (ECR) into valuable products such as formate is a compelling approach to managing excessive CO2 emissions. Tin (Sn)-based catalysts have been used for selective CO2 reduction to formate. However, they are often unstable for long-term ECR operation, especially at high reaction rates. In this work, we report highly selective Sn-based catalysts for CO2 reduction to formate at high current densities. The catalysts were prepared by depositing a layer of Sn nanoparticles on the surface of sputtered Ag on a polymer membrane. The catalysts exhibited over 90% Faradaic efficiency toward formate in the current density range of 50–300 mA/cm2 and were stable for over 20 h at a current density of 100 mA/cm2. Characterization of catalysts after ECR reaction reveals significant changes in catalyst morphology during ECR. To extend ECR operation time, we developed an in-situ catalyst regeneration strategy in which the catalysts are periodically oxidized during the reduction reaction. Using this approach, the operation time of Sn-catalysts was extended to more than 150 h with a selectivity over 90%, at the current density of 100 mA/cm2.