Effect of Zn Vacancies in Zn₃In₂S₆ Nanosheets on Boosting Photocatalytic N₂ Fixation

Abstract

Photocatalytic nitrogen fixation is considered as a very promising technology to solve the high-energy consumption problem in industrial ammonia synthesis. Because of the mildness of reaction conditions, its development is still limited by the low reaction efficiency and unknown reaction mechanism. Inspired by the mechanism of biological nitrogen fixation in nature, Zn3In2S6 with different sulfur sources is prepared to study the effects of cation defects on the adsorption, activation, and reaction in photocatalytic nitrogen fixation. Because of the electron-rich property of zinc vacancies in Zn3In2S6 nanosheets, it can effectively activate the N≡N triple bond, thereby increasing the rate of kinetic reduction. With the activation of N2 molecules on zinc vacancies, the existing protons obtained from methanol (solvent) will greatly accelerate the electron transfer between interfaces during the nitrogen reduction reaction. Notably, Zn3In2S6 with rich Zn vacancies exhibits higher activity (355.2 mg L–1 gcat–1, 15 times) than Zn3In2S6 with poor vacancies in nitrogen fixation. This work describes the contribution of zinc vacancies to the fixation and activation of nitrogen molecules, which is very important to establish a highly effective system of photocatalytic nitrogen fixation.