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.