Electrochemical reduction of CO2 on pure and doped Cu2O(111).

Cu2O has been demonstrated to be effective for converting CO2 into value-added products. However, the mechanism of the carbon dioxide reduction (CO2R) on the most stable surface, Cu2O(111), is still under debate. Additionally, how to improve its activity and selectivity is a challenging issue too. In this work, we unravel that CO2R can occur before Cu2O reduction (Cu2O-R) when the applied potential is below -0.44 V and doping can improve its catalytic performance based on first-principles calculations. The pure Cu2O(111) surface shows high activity and selectivity for the production of formic acid (HCOOH). However, the performance of CO2R deteriorates on the reduced Cu2O(111). Doping p-block elements (Al, Ga, In, Tl, Sn, Pb, Bi) is proven to be a workable strategy to improve its catalytic performance by suppressing hydrogen evolution reaction (HER). Importantly, Ga-Cu2O exhibits the favorable bonding strength for *OCHO, which is responsible for the optimal catalytic activity (-0.18 V) among other p-block elements. Our calculations thus provide an insight into CO2 reduction mechanism of Cu2O(111), favoring rational design of Cu2O-based catalyst.