Theoretical insight into effect of doping of transition metal M (M = Ni, Pd and Pt) on CO2 reduction pathways on Cu(111) and understanding of origin of electrocatalytic activity

The effect of the doped transition metal M (M = Ni, Pd and Pt) on CO2 reduction pathways and the origin of the electrocatalytic activity are investigated systematically by focusing on the CH4 and CH3OH formation pathways based on DFT calculations associated with the computational hydrogen electrode model. Our studies show that the doping of Ni, Pd and Pt can promote CO2 reduction into hydrocarbons and influence the selectivity of reduction pathways, in which the doping of Pt may be able to lead to the strongest catalytic activity. The adsorption behavior between reaction intermediates and surfaces is crucial and the interactions of intermediates with the catalysts should be moderate in order to efficiently catalyze CO2 reduction into CH4 and CH3OH, and avoid OH surface poisoning. The enhanced electrocatalytic activity of transition metal-doped Cu(111) surfaces may be owing to decreased overpotential and moderate electronic interactions between Cu and the doped transition metals. The doped Ni, Pd and Pt atoms can considerably decrease the overpotential and remove surface OH poisoning, in which the doped Pt can simultaneously reduce overpotential for CO formation and further reduction, and most easily remove OH, thus suggesting the best electrocatalytic activity. The moderate electron interaction between Cu and Pt and moderate upshift of the d-band center of Pt also explain why the Pt-doped Cu(111) surface has the best electrocatalytic activity for CO2 reduction. Two possible descriptors can be proposed in order to scale the electrocatalytic activity of Cu-based electrocatalysts for CO2 reduction, in which an ideal Cu-based electrocatalyst should be able to reduce barriers for CO formation and further reduction, and should have moderate electron interactions between Cu and the doped transition metals, and a moderate upshift of d-band center of the doped transition metals. In these ways, CO2 reduction pathways can be facilitated and the yield of hydrocarbons CH4 and CH3OH can be enhanced.