Direct Carbonate Reduction on Sn Oxide Surface.

Direct reduction of carbonate (CO32‒) to value-added chemicals presents several advantages for integrating CO2 capture from air with electrochemical conversion at near-unity efficiency. However, a critical challenge lies in effectively adsorbing CO32‒ as a reactive intermediate for sequential reduction. Density functional theory calculations indicate that the presence of oxygen vacancies (VO) on a SnO2 surface significantly enhances its reactivity toward CO32‒ adsorption, with the resulting adsorbed species (*CO3) detectable by Raman spectroscopy. Operando electrochemical Raman spectra have confirmed the formation of *CO3 on the partially reduced SnO2-xVO surface. Pulsed electrolysis has successfully converted CO32‒ to CO at a constant flow rate in an electrolyzer featuring a gas diffusion electrode configuration. A reaction cycle, encompassing SnO2 partial reduction, CO32‒ adsorption and reduction, and SnO2 regeneration, has been proposed as a viable approach for continuous direct CO32‒ reduction.