Performance Research Of TiO₂/CdS Composite Catalyst In Photocatalytic Hydrogen Production

Due to the excessive use of fossil energy,resulting in a series of problems such as energy shortage,greenhouse effect and environmental pollution,therefore,how to effectively use and produce renewable clean energy,is the focus of global researchers concerned.As a new type of hydrogen production technology,utilizing the abundant solar energy in nature to photocatalytic decompose water for hydrogen production is one of the best ways to solve energy and environmental problems.Solar photocatalytic decomposition of water for hydrogen production is an energy conversion process that converts solar energy into chemical energy(hydrogen energy).Nowadays,the industrialization of photocatalytic decomposition of water for hydrogen production is facing two important issues:solving the efficiency and cost of photocatalytic water decomposition reaction and the process engineering of reaction systems.In terms of light response,photocatalysts can be divided into ultraviolet light responsive catalysts,visible light responsive catalysts,near-infrared light responsive catalysts,and full spectrum responsive catalysts.Cadmium sulfide(CdS)semiconductor photocatalyst material is one of the representative materials in the field of visible light absorption,while titanium dioxide(TiO2)semiconductor photocatalyst material is one of the representative materials in the field of ultraviolet light absorption.The absorption bands of the two are different,and the combination of the two can broaden the absorption range of photocatalysts,making more full use of sunlight to improve the efficiency of photocatalytic water decomposition.In photocatalytic hydrogen production,the separation of photo generated carriers is also a major challenge that affects photocatalytic performance.Supporting appropriate co catalysts can effectively achieve the separation of photo generated carriers.This paper focuses on TiO2/CdS as the research object,and combines Mo2C with TiO2/CdS to prepare Mo2C/(TiO2/CdS)composite catalyst for photocatalytic water decomposition.MoP/(TiO2/CdS)semiconductor photocatalyst was formed by loading MoP co catalyst on TiO2/CdS,and photocatalytic decomposition of water was studied on MoP/(TiO2/CdS)ternary composite catalyst.The specific research content is as follows:(1)TiO2/CdS composite catalyst was prepared by hydrothermal synthesis method.The factors that enhance the photocatalytic hydrogen production activity of TiO2/CdS were studied,and the optimal hydrogen production activity of TiO2/CdS composite catalyst can reach 3265 μmol/h/g is 3.34 times that of CdS alone and 544 times that of TiO2 alone.HRTEM proves the successful preparation of TiO2/CdS.The ultraviolet spectrum proves that TiO2/CdS composite catalyst can more fully utilize sunlight to improve the efficiency of photocatalytic water decomposition.The linear sweep voltammetry curve demonstrates that the combination of TiO2 and CdS can reduce hydrogen production overpotential.When the cathode current density of the electrode is-30mA/cm2,the overpotential of TiO2 is 0.74 V,that of CdS is 0.75 V,and that of TiO2/CdS is 0.73 V;According to electrochemical impedance spectroscopy,the Nyquist half ring of TiO2/CdS is smaller than that of individual TiO2 and CdS,indicating that TiO2/CdS can reduce the interfacial charge transfer resistance.Mo2C/(TiO2/CdS)ternary composite photocatalyst was formed by loading Mo2C on the basis of TiO2/CdS through ultrasonic impregnation,with an optimal hydrogen production activity of 16762μmol/h/g,which is 5.13 times that of TiO2/CdS.The cyclic voltammetry curve shows that the capacitance value of TiO2/CdS is 0.86 F/g,and the capacitance value of Mo2C/(TiO2/CdS)is 1.32 F/g,which is 1.53 times that of TiO2/CdS.This proves that Mo2C co catalyst can effectively increase the catalyst capacitance and store more photo generated electrons.According to the linear sweep voltammetry curve,when the cathode current density of the electrode is-30mA/cm2,the overpotential of TiO2/CdS is 0.73 V,and the overpotential of Mo2C/(TiO2/CdS)is 0.67 V.The loading of Mo2C reduces the overpotential of TiO2/CdS,which is more conducive to the hydrogen production reaction process.(2)MoP/(TiO2/CdS)ternary composite catalyst was prepared by ultrasonic impregnation method.Through photocatalytic activity testing,it was found that MoP has the highest hydrogen production activity with a loading capacity of 7.0%,and its hydrogen production can reach 19041 μmol/h/g,which is 5.83 times that of TiO2/CdS.According to the linear scanning voltammetry curve,when the cathode current density of the electrode is-10 mA/cm2,the overvoltage of TiO2/CdS is 0.79 V.After loading MoP on TiO2/CdS,the hydrogen production overvoltage of the ternary composite photocatalyst MoP/(TiO2/CdS)decreases to 0.74 V.This indicates that the formation of MoP/(TiO2/CdS)on TiO2/CdS supported by MoP cocatalyst can reduce the overvoltage potential,thereby improving the hydrogen evolution performance.The electrochemical impedance spectroscopy shows that the Nyquist semicircular ring of the ternary composite photocatalyst MoP/(TiO2/CdS)is much smaller than that of TiO2/CdS,indicating that the loading of the MoP cocatalyst reduces the interfacial charge transfer resistance between the catalysts and improves the charge transfer efficiency.The transient photocurrent intensity of the ternary composite photocatalyst is significantly increased compared to TiO2/CdS,indicating that the MoP cocatalyst has a good effect on the separation of photogenerated carriers.