Synergistic Effects of Mesoporous Structure and Oxygen Vacancies in SnO ₂ for Enhanced CO ₂ Electroreduction

Electrocatalytic CO 2 reduction (CO 2 RR) into value‐added chemicals represents a promising strategy for sustainable CO 2 utilization. This strategy relies on nanoscale structural engineering to gain desired CO 2 RR catalyst performance, which is insufficiently understood. For example, how the pore structure, defect distribution, and surface reconstruction can be used to promote catalytic activity and material stability is not clarified. Here, we investigate how mesopores and oxygen vacancies (V O ) synergistically regulate the CO 2 RR behavior of SnO 2 . Mesoporous SnO 2 (M‐SnO 2 ) synthesized hydrothermally shows enhanced mesoporosity and a higher specific surface area (59 vs. 21 m 2 g −1 ) than bulk SnO 2 (B‐SnO 2 ), achieving a Faradaic efficiency (FE) of 50.9% for formate at –1.15 V vs. reversible hydrogen electrode (RHE) and improved durability (FE loss: 13.0% vs. 55.8% after 12 h). Electrochemical analysis, in situ spectroscopy, and density functional theory (DFT) calculations reveal that mesostructure facilitates CO 2 adsorption, charge transfer, stabilizes *OCHO intermediates, and lowers the reaction energy barrier via V O in M‐SnO 2 . In addition, it is shown that mesostructure promotes formation of V O , which stabilizes the oxidation state of Sn and contributes to improved stability of the catalyst. These findings establish the synergistic roles of mesoporous structure and V O for optimizing Sn‐based CO 2 RR catalysts and offer guidance for rational design of efficient CO 2 RR electrocatalysts.