Sustainable photocatalytic fixation of nitrogen facilitated by Z-scheme charge transmission in oxygen vacancy-enriched TiO_2−x/W₁₈O₄₉/WO₃ heterostructure

Photocatalysis technology is a clean and contamination-free method that uses solar energy as an inexhaustible source of energy for NH₃ generation. Herein, TiO_{2 − x}/W₁₈O₄₉/WO₃ nanocatalysts were synthesized via a straightforward solvothermal strategy. The oxygen vacancy-enriched TiO_{2 − x}/W₁₈O₄₉/WO₃ heterostructure revealed enhanced visible-light harvesting ability, fast separation of charges, and extended surface area. Notably, the NH₃ efficiency of TiO_{2 − x}/W₁₈O₄₉/WO₃-2 nanocomposite reached a considerable level of 30701 µmol L⁻¹ g⁻¹, which was 7.99 times more than that of TiO₂ and 2.01 times greater than that of W₁₈O₄₉/WO₃ nanocatalysts. This outstanding ability was ascribed to the double Z-scheme heterojunction configuration, which noticeably extended the carriers lifetime and amplified the segregation of charges. Moreover, the finer size of nanocomposite ensured the active centers were more accessible for nitrogen molecules. Finally, the durability of the nanocomposite was confirmed after 18 h of continuous use, and the amount of NH₃ generation after six consecutive cycles of use reached 25974 µmol L⁻¹ g⁻¹. This effective, cost-efficient, and stable nanocomposite has the potential to produce NH₃ in an eco-friendly manner using abundant solar energy.