Near-Infrared-Responsive Photo-Driven Nitrogen Fixation Enabled by Oxygen Vacancies and Sulfur Doping in Black TiO2–xSy Nanoplatelets

Solar-driven nitrogen fixation is a promising clean and mild approach for ammonia synthesis beyond the conventional energy-intensive Haber–Bosch process. However, it is still challenging to design highly active, stable, and low-cost photocatalysts for activating inert N 2 molecules. Herein, we report the synthesis of anatase-phase black TiO 2– x S y nanoplatelets enriched with abundant oxygen vacancies and sulfur anion dopants ( V O -S-rich TiO 2– x S y ) by ion exchange method at gentle conditions. The V O -S-rich TiO 2– x S y nanoplatelets display a narrowed bandgap of 1.18 eV and much stronger light absorption that extends to the near-infrared (NIR) region. The co-presence of oxygen vacancies and sulfur dopants facilitates the adsorption of N 2 molecules, promoting the reaction rate of N 2 photofixation. Theoretical calculations reveal the synergistic effect of oxygen vacancies and sulfur dopants on visible–NIR light adsorption and photoexcited carrier transfer/separation. The V O -S-rich TiO 2– x S y exhibits improved ammonia yield rates of 114.1 μmol g –1 h –1 under full-spectrum irradiation and 86.2 μmol g –1 h –1 under visible–NIR irradiation, respectively. Notably, even under only NIR irradiation (800–1100 nm), the V O -S-rich TiO 2– x S y can still deliver an ammonia yield rate of 14.1 μmol g –1 h –1 . This study presents the great potential to regulate the activity of photocatalysts by rationally engineering the defect sites and dopant species for room-temperature N 2 reduction.