(206f) How Much Is Surface Dopant Enough to Maximize CO2-to-Liquid Chemicals Conversion at Industrially Relevant Current Density?

Electrochemical reduction of CO₂ (CO₂R) to valuable, carbon-neutral chemical feedstocks and storable fuels driven by renewable electricity has been recognized as one of the promising technologies to mitigate the greenhouse effect, reduce global demand for fossil fuels, create sustainable energy, and achieve net zero emission by 2050. Liquid formic acid or formate electrochemically produced via CO₂R has been identified as an economically sustainable, green hydrogen carrier and fuel that can reduce carbon footprint compared with gray fossil-based formic acid. Tremendous ongoing efforts have focused on tuning catalyst morphology, composition, structure, size of tin-based electrocatalysts to improve current density, product selectivity, and durability to approach the industrial viability (current density higher than 200 mA/cm² and lifetime beyond 1,000 hours). In this study, we discuss a simple method to introduce surface sulfur heteroatoms into SnO₂ nanoparticles that would maximize CO₂ reduction to formate/formic acid with impressively high current and selectivity. The best-in-class S-SnO₂ catalysts achieved some of the highest reported partial current densities in both H-cell and single-gap, full-cell electrolyzer configurations while sustained industrially relevant partial current density and ~80% selectivity over hours of operation. Such an outstanding performance could be attributed to the electronic structural modification and improved charge transfer upon S incorporation. Computational modeling additionally revealed that S atoms preferentially occupied the catalyst surface could increase key intermediate stabilization and lower the CO₂ reduction thermodynamic barrier. Our demonstration of how dilute S dopants beneficially impact CO₂ conversion in different cell configurations provides further design concepts of high performance CO₂R electrocatalysts.