Local solid-state processes adjust the selectivity in catalytic oxidation reactions on cobalt oxides

Abstract Transition metal oxides are excellent catalysts for selective oxidation reactions, which are a prominent source of industrially relevant chemicals. However, these reactions suffer from multiple competing reaction pathways, limiting the selectivity. Thus, it is essential to gain an understanding of the underlying processes occurring on the catalyst that affect its performance. Here we synergistically combine operando X-ray spectroscopy and operando transmission electron microscopy to unravel a network of solid-state processes that controls the catalytic properties of Co 3 O 4 in the oxidation of 2-propanol towards acetone. These include exsolution, diffusion and defect formation, which strongly distort the catalyst lattice at lower temperatures. Ultimately, they also lead to a maximum in acetone selectivity when the catalyst is trapped in a frustrated or metastable state at the onset of crystallization of the exsolved particles to CoO and void formation, which coincides with the maximum in surface cobalt oxidation state in the spinel.