Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, Institute of Environmental & Applied Chemistry,College of Chemistry, Central China Normal University, Wuhan 430079, China
Ammonia synthesis is a process of vital importance to energy, environment and lives on earth. The industrial paradigm of HarborBosch process utilizes Fe as catalyst realizing largescale nitrogen fixation. Because of the robust N≡≡N triple bond of the molecular nitrogen, this reaction (N2+3H2 = 2NH3) occurs at high pressure and temperature. In recent years, the facile and “green” alternate of photocatalytic nitrogen fixation has been paid much attention. Recently, we reported that the excess electrons in oxygen vacancies (OV) could activate molecular nitrogen effectively via ① the direct electron transfer from surface oxygen vacancy to OV adsorbed N2 on catalysts such as BiOCl and BiOBr, and ② the indirect electron donation from OV to Ru and then to N2 bonded on Ru within the K/Ru/TiO2-xHx catalyst. By embedding the OV into materials of broadspectrum light absorbance, we obtained a lightdriven reactivity comparable to that of thermal HarborBosch process using the K/Ru/TiO2-xHx catalyst, which provides a new avenue for efficient solar ammonia synthesis. In this paper, we reviewed the recent advances in defects (especially the OV) promoted photocatalytic nitrogen fixation, including the nitrogen fixation mechanism of OV within various metal oxides and the coupling effect of OV to traditional active centers such as transition metals, aiming to reach a fundamental understanding of OV based nitrogen fixation. At last, we summarize the opportunities and challenges in the photocatalytic nitrogen fixation and propose possible pathways for the design of highly efficient photocatalysts.