“…The catalytic properties of metal oxides depend sensitively on the presence and nature of defects. In the case of molybdenum oxides, a high surface oxidation state is expected to be a crucial factor for partial oxidation of hydrocarbons [7]; on the other hand, the presence of oxygen vacancies plays an important role in enhancing selectivity and reactivity by providing reactive sites [8]. Thus the ability to control quantity and type of defects present in the oxides is important, both for fundamental studies and for applications.…”