Atomic-scale cation dynamics in a monolayer VO_X/α-Fe₂O₃ catalyst

Catalytic reactions are associated with dynamical changes in the catalyst that include the oxidation state and local structural variations. The understanding of such dynamics, particularly at the atomic-scale, is of great importance for revealing the activity and selectivity of the catalyst in numerous reactions. Combining in situ X-ray absorption spectroscopy with in situ diffuse reflectance infrared Fourier transform spectroscopy, we studied the redox-induced dynamical changes for a VO_X monolayer catalyst supported on a α-Fe₂O₃ powder. The results show that several co-existing VO_X species reversibly change their V oxidation states between +5 and +4, in concurrence with a structural change from two-dimensional chains to well connected V-O-V networks. These changes are also associated with the breaking and formation of the VO vanadyl group. This combined study provides new insight into how VO_X species change during catalytic reactions, which leads to proposed atomic-scale models for the redox-induced dynamics of the catalyst.