Improved performance of electrochemical reduction of CO2 to HCOOH by Cu incorporation into the supported Au monolayer on tungsten carbide: A DFT study

•Cu1Au8/WC(0001) exhibited superior catalytic performance to CO2 reduction into HCOOH.•Incorporation of Cu into AuML/WC(0001) enhanced the electrochemical adsorption of CO2.•The intrinsic origin of the improved performance of Cu-Au alloy monolayer was uncovered.•Cu1Au8/WC(0001) was a promising bifunctional catalyst for converting CO to CO2 and reducing CO2 to HCOOH.