S-scheme heterojunction of polyfluorene derivatives coupled with ZnxCd1-xS nanoparticles for efficient and stable photocatalytic hydrogen evolution

In studying photocatalytic splitting of water, the efficiency and stability of catalysts for hydrogen evolution is a thorny problem. Conjugated polymer is a novel photocatalyst that can harness solar energy and have the advantages of high efficiency, non-toxicity and long-lasting visible light tolerance, making them a popular photocatalyst material. In this paper, the organic polyfluorene derivatives PF-((g-N3)-alt-(g-OH))/inorganic semiconductor ZnxCd1-xS composite catalyst PF-((g-N3)-alt-(g-OH))/ZnxCd1-xS (ZPF-OH) was synthesized, and the S-scheme heterojunction was successfully constructed to achieve efficient and stable hydrogen evolution. The hydrogen evolution activity of the composite photocatalytic material ZPF-OH-5 remained stable in 0.35/0.25 M Na2S/Na2SO3 solution for 60 h without replacing the sacrificial reagent. The 8.41 mmol g−1 h−1 hydrogen evolution performance of ZPF-OH-5 is 50 times higher than the case of pure ZnxCd1-xS but also 11 times higher than that of PF-((g-N3)-alt-(g-OH)) in 0.35/0.25 M Na2S/Na2SO3 solution. The apparent quantum efficiency at 400 nm has corresponded to 7.9% in 10% of lactic acid solution. In addition, the in-situ X-ray photoelectron spectroscopy irradiation and fluorescence analysis has used to explore the electron transfer path after the coupling of the two pure catalysts and to confirm the formation of S-scheme heterojunction in the composite catalysts. The optimized energy band structure and high electron transfer rate of organic-inorganic S-scheme heterojunction composite catalyst promote the H2 evolution, which shows excellent potential in stable and efficient photocatalytic hydrogen evolution.