Precisely doping the surface of tin-based electrocatalysts for improved CO2 conversion to liquid chemicals
Thuy‐Duong Nguyen‐Phan, James E. Ellis, Anantha Venkataraman Nagarajan, Bret Howard, Giannis Mpourmpakis, Douglas R. Kauffman
Abstract
Doping tin catalysts with sulfur can improve the electrochemical CO2 conversion into formate/formic acid, but the lack of composition-dependent activity trends hinders further catalyst development. Here, we precisely controlled the composition of sulfur-doped Sn catalysts to show that sulfur doping only improves CO2 conversion over a very narrow composition range, achieving maximum activity at 1.4 at% S. In situ Raman spectroscopy indicted working catalysts were in a primarily metallic state (e.g. S-Sn), and we achieved some of the highest reported partial current densities in both H-cell and full-cell electrolyzer configurations. Density Functional Theory calculations predicted S atoms preferentially occupied the catalyst surface and improved CO2 reduction by localizing charge density at the catalyst/intermediate interface, which stabilized the *OCOH intermediate and lowered the CO2 conversion thermodynamic barrier. Our work quantifies the composition-dependent influence of S dopants on Sn-based CO2 reduction catalysts and provides a pathway for maximizing their CO2 conversion activity.