In situ reconstruction of defect-rich SnO2 through an analogous disproportionation process for CO2 electroreduction

Sn-based catalysts have been investigated as efficient catalysts for CO2 electroreduction toward formate production. However, they still suffer from insufficient current densities and narrow potential windows at high formate Faradaic efficiency. Herein, we developed defect-rich SnO2 (e-SnO2) with surface-covered hydroxyls groups in situ derived from SnSO4 through an analogous disproportionation process. The e-SnO2 exhibits excellent formate Faradaic efficiency over 90% at a potential range from −0.68 to −1.14 V vs. RHE. The partial current density of formate reaches 535 ± 12 mA cm−2, which is higher than that of most ever-reported Sn-based catalysts. Density functional theory calculations further reveal that the synergistic effects of oxygen vacancies and surface hydroxyls facilitate formate production by improving CO2 adsorption and balancing the energy barrier for the formation of key intermediate *OCOH.