Preparation Of Cds-based Photocatalyst And Study Of Its Electron Transfer Pathway On Hydrogen Production Performance

The energy crisis and environmental pollution are urgent issues that need to be solved in human society nowadays.Photocatalytic technology can use sunlight to carry out redox reactions,which can reduce protons to generate hydrogen and oxidize organic pollutants to degrade.Therefore,photocatalysis is a promising technology which can solve energy crisis and environmental pollution.However,the key to restricting the development of photocatalytic technology is the poor performance of photocatalysts Therefore,looking for,designing and preparing highly efficient and stable photocatalysts,as well as understanding the mechanism of photocatalyst modification is a top priority.Among the factors affecting the performance of the photocatalyst,the efficiency of photogencrated carrier separation and transfer of the photocatalyst is an important factor.Therefore,this paper wants to observe the effect of electron transfer path on the performance of photocatalyst by preparing photocatalysts with two different electron transfer paths of heterojunction structure and Z-scheme structure.This provides a guiding idea for finding new and efficient photocatalysts.The main research contents of this paper are as follows(1)Two kinds of photocatalysts,heterogeneous CdS/g-C3N4 and metal-induced Z-scheme CdS/Ag/g-C3N4,were prepared and photocatalytic hydrogen production experiments were carried out under visible light.X-ray diffraction(XRD),X-ray photoelectron spectrum(XPS),scanning electron microscopy(SEM),high resolution field emission scanning electron microscopy(HRSEM),transmission electron microscopy(TEM),UV-vis diffuse reflectance(UV-vis DRS),photoluminescence spectrum(PL),transient photocurrent and electrochemical impedance spectroscopy(EIS)were used to characterize their structure,optical and electrochemical properties.The results show that the metal-induced Z-scheme CdS/Ag/g-C3N4 photocatalyst has better photo-response performance and higher photogenerated carrier separation and transfer efficiency.The photocatalytic hydrogen production rate is 1376.0μmol/h·g,which is 1.77 times of the hydrogen production rate of the heterojunction CdS/g-C3N4(776.5 μmol/h·g)photocatalyst.The reason for this phenomenon is that the Z-Scheme structure composed of metallic Ag and metal induced photocatalysis syncrgistically promote the separation and transfer of CdS/Ag/g-C3N4 photocatalyst photogenerated carriers.(2)By controlling the metal organic framework ZIF-67 with different particle sizes,heterojunction ZIF1@CdS100,ZIF3@CdS100 and ZIF4@CdS100 photocatalyst and Z-scheme ZIF2@CdS100 photocatalyst were prepared.Photocatalytic hydrogen production experiments were carried out under visible light.X-ray diffraction(XRD),X-ray photoelectron spectrum(XPS),field emission scanning electron microscopy(FESEM),transmission electron microscopy(TEM),UV-vis diffuse reflectance(UV-vis DRS),Mott-Schottky(M-S),photoluminescence spectrum(PL),transient photocurrent and electrochemical impedance spectroscopy(EIS)were characterized.The results show that Z-scheme ZIF2@CdS 100 photocatalyst has higher photo-generated carrier separation and transfer efficiency compared with heterojunction ZIF1@CdS100,ZIF3@CdS100 and ZIF4@CdS100 photocatalysts.Its photocatalytic hydrogen production rate is 17196.56μmol/h-g,which is 3.78 times of the most excellent ZIF3@CdS100 photocatalyst(4542.81 μmol/h·g).The reason for this phenomenon is that the photo-generated carrier separation and transfer efficiency of the Z-Scheme structure electron transfer path is higher than that of the general heterojunction.