Surface-layer bromine doping enhanced generation of surface oxygen vacancies in bismuth molybdate for efficient photocatalytic nitrogen fixation

The oxygen vacancy (Ov) in photocatalysts plays a significant role for N2 fixation, but effective and simple means for creation of Ov are in urgent demand. Herein, surface-layer Br doping was confirmed to create massive surface Ov in Bi2MoO6 in a solvothermal process, with the product (BMO-Br-Ov) exhibiting remarkably enhanced N2 chemisorption and activation, photoinduced charge separation, and thus photocatalytic N2 fixation, compared with bulk Bi2MoO6, with an apparent quantum yield at 420 nm reaching 0.52% in pure water and 2.56% in the methanol aqueous solution. The charge separation enhancement benefits from the Ov introduced defect level and Br doping and surface Ov modification induced band-level difference between the surface and the inside in BMO-Br-Ov that leads to fabrication of the surface/inside homojunction. This work provides a simple way to create surface Ov in Bi2MoO6 and may direct Ov creation in other Bi-based photocatalysts for efficient N2 fixation.