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.