Study On The Design And Synthesis Of Sulfide-based Composite Photocatalytic Materials For Hydrogen Production From Photocatalytic Water Splitting

Although the technology has been singnificantly developed,the main energy used in the society is still fossil energy.However,the massive consumption of fossil resources has resulted in energy shortages and environmental pollution on a global scale.Hence,it is urgent for us to develop renewable and eco-friendly energy resources.Among them,solar energy is the largest exploitable resource while hydrogen is a renewable and clean energy with high combustion heat.Using the abundant and cheap water as raw material,the semiconductor-based photocatalytic technology can be employed to produce clean hydrogen energy from water splitting under the irradiation of sunlight,which not only provides a new idea for solving the increasing energy and environmental problems but also promotes the industrialization of hydrogen energy.However,considering the practical application process,the lower quantum efficiency of the catalyst still seversly restricts the commercial application of hydrogen production technology from photocatalytic water splitting.Hence,the development and construction of semiconductor photocatalytic materials with high catalytic activit is still extremely important.In this paper,three types of sulfide-based semiconductor photocatalytic materials(Cu₂?OH?₂CO₃/Zn_0.5Cd_0.5S,MoS₂/RGO/Mn_0.5Cd_0.5S,Mn_0.5Cd_0.5S/WO₃/Au)were prepared by different synthesis methods.The relationships between the morphology-structure-properties of the obtaimed photocatalytic materials were investigated by XRD,TEM,XPS techniques.In combination with electrochemical and photocatalytic results for photocatalytic water splitting,some suitable operating parameters have been obtained in this paper.In addition,the present study may provide theoretical basis and technical support for preparation of other heterojunction semiconductor photocatalysts with excellent performance.The main contents are as follows:?1?The binary Cu₂?OH?₂CO₃/Zn_0.5Cd_0.5S composite photocatalysts were synthesized by a simple one-step in-situ deposition method.The effects of loading amount of Cu₂?OH?₂CO₃ cocatalysts on the H₂-production performance were investigated via photocatalytic water splitting.The results indicated that the best H₂-production efficiency of 275.7?mol h^-1 could be obtained when the loading amount of Cu₂?OH?₂CO₃ reached 5 wt%,which is 3.04 times higher that of pure Zn_0.5Cd_0.5S.The enhanced photocatalytic performance can be mainly ascribed to the introduction of Cu₂?OH?₂CO₃ cocatalyst,which can accelerate the transfer rate of the photogenerated electron on the conduction band of Zn_0.5Cd_0.5S,lowers the recombination of photogenerated electron-hole pairs and simultaneously reduces the overpotential of Zn_0.5Cd_0.5S.Moreover,the introduction of Cu₂?OH?₂CO₃ cocatalyst to the photocatalytic system results in the improvement of the stability and recycling of the composite photocatalyst,thus improving the potential industrial applications.?2?The MoS₂/RGO/Mn_0.5Cd_0.5S composite photocatalysts were prepared by hydrothermal method using MoS₂,GO,Cd?CH₃COO?₂·2H₂O and Mn?CH₃COO?₂·2H₂O as raw materials.Photocatalytic hydrogen production results show that the highest H₂-production efficiency(107.58?mol h^-1)can be obtained when the loading amount of RGO and MoS₂ are 1 wt%and 3 wt%,respectively,which is 4.54times higher than that of pure Mn_0.5Cd_0.5S.Based on the photoelectric analysis,the presence of RGO can increase the separation and transfer rate of electron-hole pairs,while MoS₂ acting as a cocatalyst can promote the formation of H₂ during the photocatalytic water reduction.Moreover,due to the synergistic effects between RGO and MoS₂,more active sites can be obtained for the photocatalyst,thus greatly improving the photocatalytic activity.?3?Using WO₃ and HAuCl₄ as raw materials,Mn_0.5Cd_0.5S/WO₃/Au composite photocatalysts were synthesized by hydrothermal method and mild water bath method.The photocatalytic performances of the ternary Mn_0.5Cd_0.5S/WO₃/Au with different amounts of WO₃ and Au were investigated.The results indicated that the heterojunction between Mn_0.5Cd_0.5S and WO₃ belongs to directly Z-system.And the surface plasmon resonance can be formed when the Au nanoparticles were introduced to the Mn_0.5Cd_0.5S/WO₃ composite,which can benefit the transfer of electrons on the conduction band of Mn_0.5Cd_0.5S and consequently reduce the recombination of photogenerated electron-hole pairs,thus further improving the photocatalytic perfotmance of Z-system Mn_0.5Cd_0.5S/WO₃/Au.