Cd and O dual-vacancy-regulated CdSSe/NiFe-LDHs Z-scheme heterojunction for visible-light-driven degradation of methylene blue.

In this study, CdSSe and NiFe-LDHs were used to fabricate a CdSSe/LDHs Z-scheme heterojunction photocatalyst containing Cd and O dual vacancies (VCd+O-CdSSe/LDHs), which was applied for the efficient degradation of methylene blue under visible-light irradiation. The XRD, SEM, TEM, and EDS results demonstrate that CdSSe nanoparticles were uniformly anchored on the surface of NiFe-LDHs nanosheets, forming a tightly coupled particle-nanosheet heterointerface. XPS and ESR analyses further confirmed the stable coexistence of Cd and O dual vacancies in the composite system. These vacancies induced electron depletion on the CdSSe side and electron enrichment on the NiFe-LDHs side, indicating pronounced electron redistribution at the heterointerface. After contact between VCd-CdSSe and VO-LDH, an internal electric field directed from VCd-CdSSe to VO-LDH can be established, which promotes the selective recombination of photogenerated electrons in the conduction band of VO-LDH with holes in the valence band of VCd-CdSSe, thereby constructing a direct Z-scheme charge transfer pathway. This pathway simultaneously preserves the strongly reducing electrons in the conduction band of VCd-CdSSe and the strongly oxidizing holes in the valence band of VO-LDH. Under neutral conditions with 15 mg of catalyst and 50 mL of 10 mg L-1 MB solution, VCd+O-CdSSe/LDHs achieved an MB removal efficiency of 95.55% after visible-light irradiation. The degradation intermediates, possible degradation pathways and the toxicity prediction results were systematically investigated using LC-MS and T.E.S.T.