Defects and interface states related photocatalytic properties in reduced and subsequently nitridized Fe3O4/TiO2

The Fe 3 O 4 @TiO 2 catalyst was reduced in a mixed H 2 /N 2 atmosphere at temperatures of 400, 600, 800 and 1000   °C in order to produce the oxygen vacancies (O v ) and Ti 3+ ; Simultaneously, Fe 3 O 4 was reduced to Fe, a strongly magnetic material, beneficial for the magnetic separation after the photo-degradation. The optimal catalyst was obtained at the reducing temperature of 800   °C, which possesses the good photocatalytic performance and recycled activities; Moreover, its saturation magnetization M s is highest, reaching 23.8   emu   g −1 which improves the magnetic separability. This optimal catalyst was subsequently treated in the NH 3 atmosphere at temperatures of 500, 600 and 700   °C, aiming to investigate the effects of N-doping in TiO 2 . The 600   °C treated catalyst exhibited the optimal photocatalytic performance. The factors that affect the photocatalytic performance are revealed and discussed in detail, including the ratio of O v and N dopant in TiO 2 as well as the interface states between TiO 2 and the magnetic particles.