Boosted photocatalytic nitrogen fixation by bismuth and oxygen vacancies in Bi 2 MoO 6 /BiOBr composite structures

Photocatalytic nitrogen fixation performance is mainly hampered by slow carrier transport and inefficient surface reaction, where surface oxygen vacancies have been proved to alleviate these limitations. However, there are a few reports on the introduction of metal vacancies into photocatalysts and the effect of metal vacancies on the N 2 photofixing properties. Herein, we injected bismuth vacancies (V Bi ) into the surface of BiOBr nanospheres with oxygen vacancies (V O ) via an ion exchange strategy to form hierarchical Bi 2 MoO 6 /BiOBr composite structures. The intentionally introduced V Bi adjust the band structures of V O –BiOBr and act as charge separation centers in coordination with V O , which improves the separation efficiency of electron–hole pairs. The presence of V Bi and the Bi 2 MoO 6 phase enhances the light absorption of the composite materials. Additionally, the hierarchical nanosheet assembly structure facilitates the surface adsorption and activation of N 2 on the catalyst. In particular, the optimal defect-rich Bi 2 MoO 6 /V Bi+O –BiOBr exhibits the best photocatalytic ammonia production activity. After two hours, the NH 3 yield was 412.18 mol L −1 without any noble metal cocatalyst and sacrificial agent, and was nearly 4 times higher than that of the original V O –BiOBr (96.08 mol L −1 ). This work provides a new inspiration for the design of efficient N 2 immobilizing photocatalysts through synergistic metal and oxygen vacancy engineering.