Switching of a type I to an all-solid-state Z-scheme heterojunction by an electron mediator rGO bridge: 18.4% solar-to-hydrogen efficiency in n-ZnS/rGO/p-Bi2S3 ternary catalyst

The problem of charge transport at incomplete contact interfaces within heterogeneous junction particles remains unresolved. This study experimentally demonstrates that rGO, an electron transport mediator between p and n-type semiconductors with a Type I band arrangement, connected between the contact interfaces, promotes the diffusion of charge carriers and completely separates them. An independent assessment method is used to confirm the role of the rGO. The photoelectrocurrent coupled between the two external circuits increases the presence of rGO more significantly in n-type parallel to p-type, as compared with n-type ||n-type or p-type parallel to p-type, electrodes. The fabricated n-ZnS/rGO/p-Bi2S3 ternary catalyst absorbs the light wavelength widely, diffuses and separates the photoinduced charge carriers rapidly and strongly, and recombines e(-) and h(+) more slowly. Additional center dot OH and center dot O-2(-) radicals gather at the valence band of n-ZnS and conduction band of p-Bi2S3 during water splitting, respectively. The n-ZnS/rGO/p-Bi2S3 catalyst produces 2523.4 mu mol g(-1) h H-1(2) under simulated solar irradiation, corresponding to an 18.4% solar-hydrogen efficiency. Furthermore, the possibility of using it as an OER electrode is confirmed. Ultimately, this study reveals that the n-ZnS/p-Bi2S3 particle with a Type I band arrangement before contact is converted into a typical all-solid-state Z-scheme after the junction by bridging the rGO electron mediator. Eventually, the rearranged band diagram facilitates charge transfer, inhibits the recombination of excitons, and significantly enhances the catalytic activity.

Automated summary

The use of rGO as an electron transport mediator enhances the diffusion and separation of charge carriers in heterogeneous junction particles, improving the efficiency of photocatalysts. By optimizing band structures, exciton recombination is effectively inhibited, leading to enhanced catalytic activity.