Modeling CO₂ Hydrogenation to Methanol on an Ensemble of Inverse ZrO₂ on Cu Catalytic Sites: Mechanism, Reactivity,...

Inverse ZrO₂/Cu catalysts, where Zr oxide is deposited on Cu particles, show a high catalytic performance converting CO₂ to methanol. We employ density functional theory (DFT) calculations to investigate the CO₂ hydrogenation reaction mechanisms on a model of highly dispersed Zr oxide clusters on Cu (111). The exploration is not performed on a single active site configuration but across an ensemble of 83 formate configurations accessible under reaction conditions. Detailed reaction-pathway analysis reveals that structural sensitivity is pronounced, and only 10 of the catalyst configurations are significantly active across the full pathway. The turnover frequency of the studied inverse structures is largely determined by reaction steps after methoxy formation, rather than the formate hydrogenation steps, and the energy of the methoxy intermediate is a key reactivity descriptor. Two hypotheses are presented for the ensemble average activity: where the probabilities of site populations are determined at the formate intermediate, or at the methoxy resting state. The latter, compared to the former, drastically changes the site distribution, eliminating active structures and decreasing the average rate by a factor of 1000. Catalyst rigidity helps maintain activity by slowing down the structural evolution from the more active formate-bound states to the less active methoxy-bound states.