Insight into the effects of electronegativity on the H2 catalytic activation for CO2 hydrogenation: four transition metal cases from a DFT study

Abstract

The choice of CO₂ hydrogenation for improving product selectivity is closely related to the type of active H species on the catalyst surface. Herein, we report a density functional theory (DFT) study on H₂ activation and CO₂ pre-hydrogenation over four transition metal surfaces, i.e., Fe(111), Ni(111), Ru(0001) and Pt(111), to reveal the effect of metal electronegativity on the path choice of CO₂ hydrogenation. Metal electronegativity dominates the type of active H species on transition metal surfaces. Negative H⁻ (1s²) from H₂ dissociation on Fe(111) prefers to combine with the C-site of CO₂ benefiting for the C-terminal hydrogenation, and positive H⁺ (1s⁰) from H₂ dissociation on Pt(111) prefers to combine with the O-site of CO₂ benefiting for the O-terminal hydrogenation. The selective hydrogenation on Ni(111) and Ru(0001) are affected by CO₂ activation due to their close electronegativity to that of H. This study reveals the effect of electronegativity on the selective hydrogenation of CO₂, which is helpful to design new catalysts for the hydrogenation of CO₂ to value-added chemicals.