Ab initio study of the adsorption properties of CO2 reduction intermediates: The effect of Ni5Ga3 alloy and the Ni5Ga3/ZrO2 interface.

Abstract

The Ni5Ga3 alloy supported on ZrO2 is a promising catalyst for the reduction of CO2 due to its higher selectivity to methanol at ambient pressure, e.g., activity comparable to industrial catalysts. However, our atomistic understanding of the role of the cooperative effects induced by the Ni5Ga3 alloy formation and its Ni5Ga3/ZrO2 interface in the CO2 reduction is still far from satisfactory. In this work, we tackle these questions by employing density functional theory calculations to investigate the adsorption properties of key CO2 reduction intermediates (CO2, H2, cis-COOH, trans-COOH, HCOO, CO, HCO, and COH) on Ni8, Ga8, Ni5Ga3, (ZrO2)16, and Ni5Ga3/(ZrO2)16. We found that Ni containing clusters tended to assume wetting configurations on the (ZrO2)16 cluster, while the presence of Ga atoms weakens the adsorption energies on the oxide surface. We also observed that CO2 was better activated on the metal-oxide interfaces and on the oxide surface, where it was able to form CO3-like structures. Meanwhile, H2 activation was only observed on Ni sites, which indicates the importance of distinct adsorption sites that can favor different CO2 reduction steps. Moreover, the formation of the metal-oxide interface showed to be beneficial for the adsorption of COOH isomers and unfavorable for the adsorption of HCOO.