Origin of the volcano-like ethanol oxidative dehydrogenation activity trend for VOx/CeO2 catalysts uncovered by operando time-resolved XAS

Supported vanadia (VOx) is a versatile catalyst for various redox processes, where ceria-supported VOx have shown to be particularly active in oxidative dehydrogenation (ODH) of alcohols. In this work, we clarify the origin of the volcano-shaped ethanol ODH activity trend for VOx/CeOx catalysts using operando quick V K- and Ce L3- edge XAS experiments performed under transient conditions. We quantitatively demonstrate that both vanadium and cerium are synergistically involved in alcohol ODH. The concentration of reversible Ce4+/Ce3+ species was identified as the main descriptor of the alcohol ODH activity. The activity drop in the volcano plot, observed at above ca. 3 V/nm2 surface loading (ca. 30% of VOx monolayer coverage), is related to the formation of spectator V4+ and Ce3+ species, which were identified here for the first time. These results might prove to be helpful for the rational optimization of VOx/CeO2 catalysts and the refinement of the theoretical models.