Enhancement of built-in electric field strength of BiOCl/NMT Z-scheme heterojunctions through photoinitiated defects for optimized photocatalytic performance†

Facilitating carrier migration within Z-scheme heterojunctions is essential for improving the efficiency of photocatalytic nitrogen fixation. Herein, we successfully constructed BiOCl/NMT Z-scheme heterojunctions by a simple solvothermal process and adsorption–deposition methods. Under photoinitiation, BiOCl quantum dots could be transformed into defective structures with more oxygen vacancies. Increasing the concentration of oxygen vacancies in BiOCl not only altered the energy band structure, but also further modulated the position of the Fermi energy level (E_f). The downward migration of the E_f of BiOCl enhanced the built-in electric field (BEF) strength between it and NMT, which enabled the rapid separation and migration of photogenerated carriers. 0.05-BiOCl/NMT expressed optimal nitrogen reduction performance along with NH₃ generation at a rate of 88.6 μmol g⁻¹ h⁻¹. The nitrogen fixation rate of 0.05-BiOCl/NMT was 8.5 and 2.7 times higher than that of BiOCl and NMT. This work adjusted the BEF intensity by a straightforward self-conversion to a defective structure, which offered fresh insights into the promotion of carrier separation in photocatalytic nitrogen fixation.