Black reduced porous SnO2 nanosheets for CO2 electroreduction with high formate selectivity and low overpotential

The great bottleneck that lies in CO2 reduction reaction (CO2RR) electrocatalysts is to simultaneously enhance their conductivity and density of active sites. Herein, we developed a black reduced porous SnO2 nanosheets electrocatalyst that enabled possessing both metallic conductivity and high density of active sites via vacancy engineering. The black reduced porous SnO2 nanosheets showed high activity and selectivity for CO2RR to formate, with maximum Faradaic efficiency (FE) of 92.4% at the low overpotential of 0.51 V and stable FE of 90 ± 2% in the large potential range from -0.6 to -1.1 V vs. reversible hydrogen electrode (RHE). Density functional theory (DFT) calculations indicated that the introduction of oxygen vacancy increased carrier density and lowered the adsorption of HCOO- * and HCOOH by 0.29 and 0.17 eV, respectively, accounting for the improved CO2RR to formate performance.