Efficient photocatalytic nitrogen fixation under ambient conditions enabled by the heterojunctions of n-type Bi2MoO6 and oxygen-vacancy-rich p-type BiOBr

Abstract

N₂ fixation is one of the most important chemical reactions in the ecosystem of our planet. However, the industrial Haber–Bosch ammonia synthesis process is restricted by harsh reaction conditions (350–550 °C, 150–350 atm) and undesirable environmental effects (a large amount of CO₂ emission). Photocatalytic N₂ fixation is promising for achieving sustainable ammonia synthesis under ambient conditions with lower energy input and less environmental issues. However, the known photocatalysts for N₂ reduction under mild conditions still face the great challenge of very low energy conversion efficiency. Herein, we report a facile solution-phase method to prepare the heterojunctions based on n-type Bi₂MoO₆ nanorods and oxygen-vacancy-rich p-type BiOBr nanosheets (Bi₂MoO₆/OV-BiOBr). Originating from the formation of p–n junctions and suitable bandgap configuration, the Bi₂MoO₆/OV-BiOBr heterojunctions exhibit effective light utilization and photogenerated electron–hole separation properties. Moreover, it is confirmed that the oxygen vacancies on BiOBr nanosheets are propitious to the adsorption and activation of N₂ molecules. Benefiting from these merits, the Bi₂MoO₆/OV-BiOBr heterojunctions exhibit improved photocatalytic performance for N₂ conversion to ammonia without any noble metal co-catalysts and sacrificial reagents under ambient conditions.