A DFT study of CO2 electrochemical reduction on Pb(211) and Sn(112)

Electrochemical reduction of CO₂ has the benefit of turning greenhouse gas emissions into useful resources. We performed a comparative study of the electrochemical reduction of CO₂ on stepped Pb(211) and Sn(112) surfaces based on the results of density functional theory slab calculations. We mapped out the potential energy profiles for electrochemical reduction of CO₂ to formate and other possible products on both surfaces. Our results show that the first step is the formation of the adsorbed formate (HCOO*) species through an Eley-Rideal mechanism. The formate species can be reduced to HCOO^? through a one-electron reduction in basic solution, which produces formic acid as the predominant product. The respective potentials of forming HCOO* are predicted to be ?0.72 and ?0.58 V on Pb and Sn. Higher overpotentials make other reaction pathways accessible, leading to different products. On Sn(112), CO and CH₄ can be generated at ?0.65 V following formate formation. In contrast, the limiting potential to access alternative reaction channels on Pb(211) is ?1.33 V, significantly higher than that of Sn.