Efficient photocatalytic H2 evolution over NiS-PCN Z-scheme composites via dual charge transfer pathways

In this study, both narrow band-gap semiconductor NiS and S and O defects modification were introduced into the design of PCN photocatalyst to enhance its photocatalytic performance. The O and S defects, on one hand, provided the higher specific area and more charge separation sites, and constituted the dual fast charge transfer pathways with NiS through the N-C-S-Ni bonds and N-C-O-Ni-S bonds, which greatly increased the carrier transfer kinetics at the interface and restricted the carrier recombination. On the other hand, the midgap level derived from S and O defects also enhanced the absorption of visible light and accommodated more excited electrons. Furthermore, Z-scheme mode could form as Ni2+ species were reduced to metallic Ni-0 to acts as charge transfer mediator under irradiation. As such, a maximum hydrogen evolution rate of 1239.3 mu mol/g/h was achieved over 5%NiS/SO-Melon composite, nearly 31.4 times the rate of pristine PCN.