Porphyrin Conjugated Polymer Grafted onto BiVO4 Nanosheets for Efficient Z-Scheme Overall Water Splitting via Cascade Charge Transfer and Single-Atom Catalytic Sites

This work shows a novel artificial Z-scheme photosystem based on a heterometallic Zn-/Pt-porphyrin conjugated polymer (ZnPtP-CP) grafted onto ultrathin BiVO4 nanosheets via Zn-O-V bridging bonds for high-efficiency overall water photosplitting. An impressive apparent quantum yield of 9.85% at lambda = 400 nm is achieved over the resulting ZnPtP-CP/BiVO4 composite, in which BiVO4 nanosheets are in close contact with ZnPtP-CP nanosheets via Zn-O-V bridging bonds to promote a Z-scheme charge transfer mechanism with ZnPtP-CP serving as electron-rich unit and BiVO4 as hole-rich one. The photoexcited electrons of BiVO4 transfer to the interface and recombine with the photogenerated holes of ZnPtP-CP through the Zn-O-V bonds, and thus the strong reducibility of the photoinduced electrons in ZnPtP-CP and the strong oxidation ability of the photogenerated holes in BiVO4 are maintained. Moreover, the highly dispersed Pt centers (PtN4) in Pt-porphyrin bridging units act as single-atom catalytic sites to facilitate a cascade charge transfer by fast migration of the photogenerated electrons from Zn-porphyrin to Pt-porphyrin units for the water reduction reaction. This Z-scheme mechanism with two-step excitation and cascade charge transfer pathway makes the composite acting as Z-scheme dual-function photocatalyst responsible for the efficient solar-driven overall water photosplitting without the aid of a sacrificial reagent or external bias.

Automated summary

This work demonstrates a highly efficient overall water photosplitting through the combination of heterometallic Zn-/Pt-porphyrin conjugated polymer and BiVO4 nanosheets. The Z-scheme charge transfer mechanism facilitated by Zn-O-V bridging bonds enables dual functionality in the catalyst and cascade charge transfer with Pt centers.