Direct observation of oxygen-vacancy formation and structural changes in BiWO nanoflakes induced by electron irradiation.

The prominent role of oxygen vacancies in the photocatalytic performance of bismuth tungsten oxides is well recognized, while the underlying formation mechanisms remain poorly understood. Here, we use the transmission electron microscopy to investigate the formation of oxygen vacancies and the structural evolution of BiWO under in situ electron irradiation. Our experimental results reveal that under 200 keV electron irradiation, the breaking of relatively weak Bi-O bonds leads to the formation of oxygen vacancies in BiWO.