Study On Photogenic Charge Transfer Mechanism And Hydrogen Production Performance Metal Sulfide Based Photocatalyst

Metal sulfide semiconductor is considered as one of the most promising photocatalysts because of its strong optical response,low cost,easy preparation and high catalytic activity.In this paper,ZnCdS,a solid solution,is studied and compared by means of regulation and control to find the most efficient photocatalyst and construct S-scheme heterojunction to explore its effect on photocatalytic hydrogen production.The main research contents include the following aspects:1.In this paper,a typical solvothermal method is used to prepare Zn_0.7Cd_0.3S,and non-noble metal Ni nanoparticles are loaded on Zn_0.7Cd_0.3S by in-situ light deposition.When the composite catalyst is placed in a Na₂S/Na₂SO₃ solution,the hydrogen production rate can be as high as about 12 mmol h^-1g^-1.As the co-catalyst and active site of the reaction,Ni metal nanoparticles greatly improved the electron transfer rate,thereby inhibiting the recombination of electron-hole pairs and improving the photocatalytic activity.2.The change of the mole ratio of metallic elements and nonmetallic elements will affect the morphology and structure of ZnCdS,and further affect the separation and hydrogen production capacity of photoelectron-hole pairs.In this study,the morphology of ZnCdS is adjusted by changing the molar amount of thioacetamide.The structures of the samples are analyzed by X-ray diffraction,transmission electron microscope,X-ray photoelectron spectroscopy and physical adsorption-desorption instrument,and their optical properties,photocatalytic hydrogen production capacity and photoelectrochemical performance are evaluated.With the increase of thioacetamide dosage and the increase of crystallinity,ZnCdS nanorods self-assemble into nanorods,and the number of defects decreases.When the molar ratio of（Zn+Cd）:S is 1:3.5,the photocatalytic activity is the highest,about 12.57 mmol h^-1g^-1,which is 6.2 times higher than that when the molar ratio of（Zn+Cd）:S is 1:1.One-dimensional nanorods contribute to the formation of space charge regions and guide charge carriers along the nanorods.Self-assembled ZnCdS nanocrystals provide additional channels for charge transfer,thereby enhancing electron-hole pair separation and promoting photocatalytic activity.3.Pure NiS₂,MoSe₂ and NiS₂/MoSe₂ are prepared by typical solvothermal method.The optical and electrical properties of S-scheme heterojunction NiS₂/MoSe₂ and the photocatalytic hydrogen production capacity are studied systematically.In addition,in the Eosin-Y（EY）-sensitized photocatalytic system,EY,as a photosensitizer,effectively enhances the light absorption efficiency,so as to promote the light reaction.The establishment of S-scheme heterojunction is helpful to improve the redox capacity of the reaction system and enhance the hydrogen production activity of catalyst NiS₂/MoSe₂,which is about 7 mmol h^-1g^-1,2.05 times and 2.44 times of the hydrogen production activity of pure NiS₂ and MoSe₂,respectively.High electron-hole separation rate and fast electron transfer efficiency are the main reasons to improve the efficiency of photocatalytic hydrogen evolution reaction.This study provides a new strategy for constructing S-scheme heterojunctions of narrow-band gap semiconductors for direct application in photocatalytic hydrogen evolution systems.