Synergistic Tuning\nof Heterovalent States and Oxygen-Vacancy\nDefect Engineering in Hydrophilic W‑Doped Sb<sub>2</sub>OS<sub>2</sub> for Enhanced Nitrogen Photoreduction to Ammonia

Nitrogen fixation reaction via photocatalysis offers\na green and\npromising strategy for renewable NH<sub>3</sub> synthesis, and catalysts\nwith high-efficiency photocatalytic properties are essential to the\nprocess. Herein, we demonstrate a W-doped Sb<sub>2</sub>OS<sub>2</sub> bimetal oxysulfide catalyst (labeled as SbWOS) with abundant oxygen\nvacancies, heterovalent metal states, and hydrophilic surfaces for\nnitrogen photoreduction to ammonia. The SbWOS-3 with suitable W-doping\nexhibited excellent nitrogen fixation activity of 408.08 μmol·g<sup>–1</sup>·h<sup>–1</sup> and an apparent quantum\nefficiency (AQE) of 1.88% at 420 nm and a solar-to-ammonia (STA) conversion\nefficiency of 0.082% in pure water under AM1.5G light irradiation.\nThe W-doping not only transforms hydrophobic Sb<sub>2</sub>OS<sub>2</sub> into a hydrophilic catalyst, making it easier for H<sub>2</sub>O molecules adsorbed on the SbWOS surface and catalyzed into protons,\nbut also endows the SbWOS catalyst with rich oxygen vacancies, acting\nas the active sites for trapping and activating the N<sub>2</sub> molecule,\nand for trapping and activating H<sub>2</sub>O to produce the protons\nfor the N<sub>2</sub> photocatalytic reduction reaction. The hydrazine\ndrives the SbWOS catalyst with the heterovalent metal states, which\nacts as the photogenerate electrons quickly hopping between W<sup>5+</sup> and W<sup>6+</sup> to transfer for the N<sub>2</sub> reduction\nreaction. This study provides a feasible scheme for applying oxygen\nvacancy defects, heterovalent metal states, and surface hydrophobic-to-hydrophilic\nwetting engineering in bimetal oxysulfide for N<sub>2</sub> photoreduction\nto ammonia.