Creation of rich oxygen vacancies in bismuth molybdate nanosheets to boost the photocatalytic nitrogen fixation performance under visible light illumination

[Display omitted] •Creation of rich oxygen vacancies in Bi2MoO6 nanosheets by NaOH etching treatment.•Enhancement of the photogenerated charge carrier separation.•Enhancement of N2 adsorption and activation capabilities.•Enhanced and stable photocatalytic N2 fixation performance under visible light.•Good tolerance to O2 existence in N2 source for the use of air to replace pure N2. There is a huge demand for ammonia worldwide due to its extensive utilization in various technical applications. However, its production is still dependent on the traditional Haber-Bosch process under high temperature and pressure, which has enormous pressure on both the world energy supply and global warming issue. In this work, bismuth molybdate nanosheets rich in oxygen vacancies were created via NaOH treatment of bismuth molybdate nanosheets by a simple, robust and cost-effective process of NaOH etching treatment at room temperature to boost the photocatalytic nitrogen fixation to produce ammonia under visible light illumination at room temperature and ambient pressure. It was found that rich oxygen vacancies largely improved both the photogenerated charge carrier separation and N2 adsorption/activation capabilities of bismuth molybdate nanosheets. Thus, an enhanced, stable photocatalytic N2 fixation performance with a superior average ammonia production rate of near 800 μmol·g−1·h−1 was achieved under visible light illumination in repeated uses. Even better photocatalytic N2 fixation performance was observed under simulated solar illumination. The photocatalyst showed good tolerance to oxygen, allowing the use of air rather pure N2 in the reaction. Thus, it is promising for ammonia production from the photocatalytic N2 fixation with solar energy by these bismuth molybdate nanosheets with rich oxygen vacancies, which could provide a greener and more sustainable alternative than the traditional Haber-Bosch process.