Ceria -Mediated Dynamic Sn0/Snδ+ Redox Cycle for CO2 Electroreduction

Electrocatalytic CO2 reduction has been considered an effective carbon neutrality as well as energy storage strategy integrated with renewable electricity. CO2 conversion to formate is a feasible route using earth-abundant and nontoxic tin-based catalysts. However, they suffer from degradation and thus decrease in formate selectivity during operation. Guided by density functional theory (DFT) calculations, herein, we synthesized CeO2–SnO2 heterostructures by a facile electrospinning method, which exhibited a maximum formate partial current density of ∼500 mA·cm–2 with 87.1% faradaic efficiency and a long-term stability in a flow cell. Proved by in situ attenuated total reflectance infrared absorption spectroscopy (ATR-IRAS) and Raman spectra as well as post-X-ray photoelectron spectroscopy (XPS) analysis, a dynamic CeO2-mediated Sn0/Snδ+ redox cycle mechanism was proposed: oxygen vacancies generated on cerium oxides prompted water dissociation to produce *OH and *H species, where the former oxidize Sn0 into active Snδ+, facilitating the conversion of CO2 to the key intermediate *OCHO with the help of the latter. This work may provide a general strategy to design stable and efficient catalysts for practical CO2 electrolyzers.