Robust route to photocatalytic nitrogen fixation mediated by capitalizing on defect-tailored InVO4 nanosheets

Abstract

Ammonia (NH₃) is one of the fundamental pillars of the chemical industry nowadays. Compared with the traditional Haber–Bosch process that requires high energy consumption, the photocatalytic conversion of N₂ to NH₃ under mild conditions is recognized as a sustainable and environmentally-friendly technology. However, the photocatalytic breakage of the NN bond in nitrogen (N₂) is a kinetically difficult process. Here, based on density functional theory (DFT) calculations, we report a novel and viable strategy to markedly boost the photocatalytic nitrogen fixation efficiency of InVO₄ by tailoring its oxygen vacancies (V_O). InVO₄ containing constructed V_O (V_O-InVO₄) shows enhanced ammonia production rate, which can be attributed to the promoted N₂ adsorption, improved N₂ activation and decreased reaction barriers on the InVO₄ surface, as evidenced by DFT simulations. Remarkably, the NH₃ yield rate of the optimal V_O-InVO₄ achieves up to 139.03 μmol g_cat⁻¹ h⁻¹, which is 5.33 times higher than that of InVO₄ without additional V_O fabrication. The introduction of V_O largely suppresses the photogenerated charge carrier recombination and enhances visible light utilization, as revealed by photoluminescence and UV-vis absorption spectra, respectively, which correlate well with simulations. Notably, the low-valence V⁴⁺ induced by V_O is a more favorable active reaction site for N₂ adsorption, as revealed by the simulation results. This study not only provides a simple yet robust strategy to craft catalysts of high efficiency for photocatalysis, but also expands the mechanistic understanding about defect-mediated catalysis.