Insights into electrochemical CO2 reduction on tin oxides from first-principles calculations

Density functional theory calculations were used to unravel the mechanism of CO2 electroreduction on SnOx surfaces. Under highly reducing conditions (< -0.6 V vs. RHE), the SnO(101) surface with oxygen vacancies is likely the active phase for CO2 reduction. We showed that the proton-electron transfer to adsorbed *CO2 forming *OCHO, a key intermediate for producing HCOOH, is energetically more favorable than the formation of *COOH, justifying the selectivity trends observed on Sn-based electrocatalysts. With linear scaling relations, we propose the free formation energy of *CO2 at the oxygen vacancy as the reactivity descriptor. By engineering the strain of the SnO(101) surface, the selectivity towards HCOOH can be further optimized at reduced overpotentials. (C) 2017, Institute of Process Engineering, Chinese Academy of Sciences. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co., Ltd.