Dual vacancies and S-scheme BiOBr/Bi2WO6 heterojunction synergistically boost the directional transfer of photogenerated electrons for efficient photocatalytic degradation of norfloxacin

Defect (vacancy) engineering is a cost-effective and efficient modification strategy for S-scheme heterojunctions. In this work, S-scheme BiOBr/Bi₂WO₆ heterojunctions with bromine vacancies (V_Br) and tungsten vacancies (V_W) were prepared by the NaOH etching method. The efficiencies of photodegradation of NOR for the optimal sample, V_W+Br-BiOBr/Bi₂WO₆–3 (V_W+Br-BBW), showed approximately 11.5 times improvement over Bi₂WO₆ and 2.7 times over BiOBr. The BrW dual vacancies generated a polarization electric field (PEF) in V_W+Br-BBW. The collaboration between the PEF and internal electric field (IEF) facilitated the directional movement of photogenerated electrons, leading to improved separation and migration of photocarriers. Owing to the synergistic effect of dual vacancies and S-scheme heterojunction, V_W+Br-BBW showed superior photocatalytic performance for NOR degradation. This work presents a possible approach to incorporating dual vacancies in heterojunctions to enhance photocatalytic performance and emphasizes the pivotal role of defects in constructing the S-scheme system.