Catalytic Activity of an Ensemble of Sites for CO2 Hydrogenation to Methanol on a ZrO2-on-Cu Inverse Catalyst

Abstract

The significant increase in CO₂ emissions from heavy fossil fuel utilization has raised serious concerns, highlighting the need for effective methods to convert CO₂ into value-added chemicals. Here, we report a computational investigation on the catalytic activity of ZrO₂-on-Cu inverse catalysts for CO₂ hydrogenation to methanol, considering highly dispersed ZrO₂ trimers on Cu (111). Such clusters present a large ensemble of formate-containing configurations, Zr₃O_n(OH)_m(OCHO)_l, making the evaluation of the catalytic activity very challenging. We found that the sites on the various catalyst configurations exhibit markedly different activities for formate hydrogenation, despite their similar free energy and composition. To understand these differences in reactivity, we examined the structural and electronic nature of the low free-energy catalyst configurations and identified that the energy of the lowest unoccupied orbital of the reacting formate, modified by its binding with the catalytic site, is a descriptor for the reaction energy of the formate hydrogenation step. From there, we screened an ensemble of catalyst structures using this descriptor to predict highly active metastable catalyst configurations and computed the reaction pathways and transition states for formate hydrogenation. From this investigation, we distinguished reactive from nonreactive sites and formate species on the ZrO₂/Cu inverse catalyst based on structural and electronic features. We showed that rare metastable configurations control the activity. Additionally, an efficient method for examining the reactivity of a large number of coexisting catalyst structures was developed.