First-Principles Insight into Electrocatalytic Reduction of CO2 to CH4 on a Copper Nanoparticle

Copper has been extensively studied for electrocatalytic CO, reduction reaction (CO2RR) due to its unique capability to produce hydrocarbons at high overpotentials. Although CO2RR on crystallographic Cu surfaces such as Cu (211) and Cu(111) has been investigated by many, the detailed mechanistic understanding of CO2RR on small Cu nanoparticles (NP) is still lacking. In this work, we use Cu-79 as a representative NP and compare it with Cu(211) and Cu(111) for reduction of CO, to CH4 by first-principles calculations. The computed free energy profiles show that the Cu-79 NP exhibits less negative onset potential for the formation of CO than both Cu(211) and Cu(111) but more negative onset potential for the formation of CH4 than Cu(211). These onset potential trends for CO and CH4 formations on Cu-79 NP, Cu(211), and Cu(111) are correlated with adsorption energetics of the key reaction intermediates including COOH, CO, and CHO. The insight may help improve the performance of Cu NPs for CO2RR to CH4.