Vacancy-Enabled Mesoporous TiO2 Modulated by Nickel Doping with Enhanced Photocatalytic Nitrogen Fixation Performance

Photocatalysis provides a sustainable route to convert N2 to NH3 with the aid of a photogenerated electron. Beyond the typical issue in the photocatalytic field, NH3 synthesis requires adsorption, activation, and hydrogenation of N2. In this report, Ni-doped TiO2 (Ni-x-TiO2) photocatalysts were fabricated by a simple sol–gel method to introduce the oxygen defects and Ni site on TiO2. The oxygen vacancy (Vo) enhances the adsorption of N2 on the catalyst surface. The Ni doping induced a defect energy level below the conduction band, which prefers to accept the photogenerated electron. The electron captured by Vo tends to transfer to the adsorbed N2 and activate N2. On the other hand, the Ni site is a typical H2 production site. It provides enough H2 for the hydrogenation of N2 to form NH3. To sum up all of these advantages, Ni-doped TiO2 displays a high NH3 production rate of 46.80 μmol·g–1·h–1 which is about 7 times higher than that of pure TiO2. This manuscript provides a potential method to design a highly efficient photocatalyst for the NH3 synthesis.