Visualizing atomic-scale redox dynamics in vanadium oxide-based catalysts

Surface redox processes involving oxygen atom exchange are fundamental in catalytic

reactions mediated by metal oxides. These processes are often difficult to uncover

due to changes in the surface stoichiometry and atomic arrangement. Here we employ

high-resolution transmission electron microscopy to study vanadium oxide supported

on titanium dioxide, which is of relevance as a catalyst in, e.g., nitrogen oxide emission

abatement for environmental protection. The observations reveal a reversible transformation

of the vanadium oxide surface between an ordered and disordered state, concomitant with a

reversible change in the vanadium oxidation state, when alternating between oxidizing and

reducing conditions. The transformation depends on the anatase titanium dioxide surface

termination and the vanadium oxide layer thickness, suggesting that the properties of

vanadium oxide are sensitive to the supporting oxide. These atomic-resolution observations

offer a basis for rationalizing previous reports on shape-sensitive catalytic properties.