Molybdenum Disulfide As Cocatalysts For Enhanced Photocatalytic Hydrogen Evolution Activity Over Sulfide Semiconductors

Semiconductor photocatalytic hydrogen evolution is one of the effective ways to transform solar energy into hydrogen.In order to realize the large-scale application of this technology,the development of photocatalytsts with visible-light-response,efficiency and stability has become the key problem in this field.In general,loading cocatalysts facilitates lowering the overpotential of the photocatalytic reaction and increasing the reactive active sites,and then enhancing photocatalytic hydrogen evolution activity.Recent studies have shown that the layered molybdenum disulfide?MoS₂?as a cocatalyst can significantly enhance the photocatalytic activity.Therefore,this study will increase the photocatalytic hydrogen evolution activity by loading MoS₂on the surface of sulfide semiconductor.The main contents and conclusions are as follows:1.The MoS₂ was loaded on the spherical CdS surface by a solvothermal method.The effects of loading contents of MoS₂ on the photocatalytic hydrogen evolution activity were comparatively investigated with 0.45 mol/L Na₂S and 0.55 mol/L Na₂SO₃as sacrificial agents.The results showed that the 5wt%MoS₂/CdS composite could achieve the highest photocatalytic H₂ evolution rate of 372?mol·h^-11 and apparent quantum efficiency?AQE?about 7.31%under 420 nm monochromatic light irradiation.The remarkably enhanced photocatalytic activity of composite could be attributed to the cocatalyst of MoS₂ facilitates the transfer and separation of photogenerated charge carriers.2.The MoS₂/Cd_0.8Zn_0.2S composites were prepared through loading MoS₂ on Cd_0.8Zn_0.2S surface by a solvothermal process.With lactic acid as sacrificial reagents,the5wt%MoS₂/Cd_0.8Zn_0.2S catalysts exhibited the best photocatalytic activity for H₂evolution with the rate of 991?mol·h^-1.It could be seen that loading MoS₂ on the Cd_0.8Zn_0.2S surface would further enhance photocatalytic hydrogen evolution performance.3.The CdMoO₄/CdS@MoS₂ ternary composites were synthesized by a one-step hydrothermal approach.The photocatalytic hydrogen evolution activities of CdMoO₄/CdS@MoS₂ ternary composites and CdMoO₄/CdS,MoS₂/CdMoO₄,MoS₂/CdS composites were compared with lactic acid as a sacrificial reagent.The results show that the CdMoO₄/CdS@MoS₂ ternary composites significantly enhance the photocatalytic hydrogen evolution activity.