Amorphous bimetallic sulfide Co9S8/SnS2 used as a p–n heterojunction to achieve photocatalytic hydrogen evolution

Abstract

The construction of semiconductor-coupled heterojunctions can effectively enhance the transport efficiency of photogenerated electrons and holes and the photocatalytic hydrogen-producing performance of catalysts. SnS₂ and Co₉S₈ were prepared by applying the hydrothermal method, and the composite catalyst Co₉S₈/SnS₂ was prepared by applying the electrostatic self-assembly method. Both SnS₂ and Co₉S₈ were amorphous monometallic sulfides, and the n-type semiconductor SnS₂ and p-type semiconductor Co₉S₈ were constructed into Co₉S₈/SnS₂ p–n type heterojunctions. Co₉S₈ irregular spheres around 400 nm were attached to SnS₂ smooth balls around 800 nm, thereby providing more reactive sites. The doping of Co₉S₈ promoted the separation of hole–electron pairs and increased the photogenerated electron and hole transfer rate, thereby effectively improving the visible photocatalytic hydrogen-producing activity of SnS₂. The 5 h hydrogen-producing amount of Co₉S₈/SnS₂ reached 120.91 μmol, which was 4.5 times that of Co₉S₈. The morphology and structure of the catalyst were explored by XRD, SEM and TEM characterization tests. The catalyst was spectrally analyzed by XPS, PL and UV-vis characterization tests, and the electrochemical aspects of the catalyst were characterized by an electrochemical test and zeta potential test. The construction of Co₉S₈/SnS₂ p–n heterojunction changes the transfer pathway of photogenerated carrier electrons, thereby promoting the hydrogen-producing performance of Co₉S₈/SnS₂, and its construction mechanism provides certain theoretical support for photocatalytic and efficient hydrogen-producing technology.