Elucidating the role of oxygen coverage in CO2 reduction on Mo2C

Abstract

Molybdenum carbide (Mo₂C) is a promising and low-cost catalyst for the conversion of CO₂ to CO. However, the underpinning mechanism occurring on the catalyst surface and the understanding of the catalyst structure under the reaction conditions is still elusive. In this study, we employ first principles calculations to understand the CO₂ dissociation mechanism on β-Mo₂C (001) under different oxygen coverage on the catalyst surface (oxycarbide). Our results demonstrate that with increasing oxygen coverage, there is an electronic modification on the catalyst surface (e.g. d-band shift on Mo atoms), that in turn, tunes the interactions of the adsorbates and the CO₂ dissociation barriers. Interestingly, we reveal linear relationships between the oxygen coverage and electronic modification with the reactivity of the catalyst. We show that CO₂ can adsorb and dissociate on the oxygen covered Mo₂C surface, even in the presence of surface oxygen up to 0.5 monolayer (ML). Our results rationalize a series of experimental observations.