Highly efficient photocatalytic nitrogen fixation of ZnWO4/g-C3N4 S-scheme heterojunction nanofibers: Synergistic effect of water molecules deprotonation and photogenerated electrons

Abstract

Photocatalytic nitrogen fixation presents a promising method for low-energy and environmentally friendly ammonia production. However, efficiency remains relatively low due to insufficient proton and electron supply during the photocatalytic process. In this study, ZnWO₄/g-C₃N₄ S-scheme heterojunction nanofibers are prepared by electrospinning combined with vapor deposition method. The ZnWO₄/g-C₃N₄ nanofibers are rich in oxygen vacancies and heterovalent W ions, which work synergistically to protonate water molecules, thereby providing the necessary protons for nitrogen fixation. The matched energy band structures of ZnWO₄ and g-C₃N₄ form a built-in electric field at contact interface, which effectively separate photogenerated carriers. The one-dimensional nanofiber structure induces the carrier transport along the fiber axis and shortens the diffuse distance for carriers to active sites. As expected, the maximum photocatalytic nitrogen fixation performance of ZnWO₄/g-C₃N₄ reaches 144.5 μmol·L^-1·min⁻¹·g⁻¹, which is 19.5 times higher than that of single-component g-C₃N₄. After five cycles of experiments, the performance is 90.8 % of the original, showing significant stability. ZnWO₄/g-C₃N₄ also exhibits excellent photocatalytic nitrogen fixation activity and stability in natural river water, with practical application potential. This innovative achievement is expected to be applied in future agricultural production, promoting agriculture towards a greener and lower-carbon direction.