Computational studies of electrochemical CO2 reduction on subnanometer transition metal clusters

Abstract

Computational studies of electrochemical reduction of CO₂ to CO, HCOOH and CH₄ were carried out using tetra-atomic transition metal clusters (Fe₄, Co₄, Ni₄, Cu₄ and Pt₄) at the B3LYP level of theory. Novel catalytic properties were discovered for these subnanometer clusters, suggesting that they may be good candidate materials for CO₂ reduction. The calculated overpotentials for producing CH₄ are in the order, Co₄ < Fe₄ < Ni₄ < Cu₄ < Pt₄, with both Co₄ and Fe₄ having overpotentials less than 1 V. Investigation of the effects of supports found that a Cu₄ cluster on a graphene defect site has a limiting potential for producing CH₄ comparable to that of a Cu (111) surface. However, due to the strong electronic interaction with the Cu₄ cluster, the defective graphene support has the advantage of significantly increasing the limiting potentials for the reactions competing with CH₄, such as the hydrogen evolution reaction (HER) and CO production.