| In the 20th century,humans for the first time purified and separated chlorophyll,the key to photosynthesis of green plants,and resolved the chemical structure of chlorophyll.To this day,exploring photosynthesis is still ongoing and the efforts are being made to achieve artificial photosynthesis.At present,the efficiency,reaction conditions and economy of artificial photosynthesis are still far inferior to the photosynthesis of green plants in nature.In photosynthesis,the most critical reaction is the decomposition of water molecules into oxygen molecules,hydrogen ions and electrons under the action of light and chlorophyll.Therefore,a series of explorations on photocatalytic/photoelectrocatalytic water splitting were carried out.In 1972,Fujishima and Honda discovered that TiO2 photoanode can decompose water to produce hydrogen under UV light irradiation.Limited by the wide band gap,TiO2 cannot make full use of the sunlight reaching the earth’s surface.Coupling TiO2 with semiconductors with visible light response and matched energy level to prepare semiconductor composite electrodes with visible light response and enhanced photoelectrochemical activity has become a hot topic in recent years.Among many semiconductor materials,metal oxide semiconductors are favored by researchers due to relatively high stability.Modifying a material with good conductivity between two kind of metal oxide semiconductor materials can promote the transfer of photo-generated carriers.Moreover,it can compensate for the weak visible light absorption of metal oxide semiconductor.Therefore,this ternary composite electrode becomes one of the optimum ways to further improve the performance of the binary composite electrode.In this work,the preparation,photoelectrichemical performance and mechanism of ternary composite electrodes were studied,and the main progress and results are as follows:1.As TiO2 nanotube arrays were prepared by anodic oxidation,TiO2 nanotube arrays with thicker wall and relatively flat surface are obtained through shortening the distance between the anode and the cathode.A certain amount of RGO were deposited on the surface of the thick-walled TiO2 nanotube arrays using pulsed electrodeposition method to obtain RGO-TiO2 nanotube array binary composite electrode.Compared with the RGO-TiO2 nanotube array electrode prepared by mainstream method,in this work,the higher reduction degree of RGO and lower preparation cost of TiO2 nanotube arrays can be achieved,which lays a good foundation for the further preparation of ternary composite electrodes based on RGO-TiO2 nanotube arrays.2.Bi2MoO6 nanoparticles with particle size of about 5 nm were synthesized by chemical precipitationand centrifugation,and loaded on the RGO-TiO2 nanotube array binary composite electrode through ultrasonic electrophoresis to obtain Bi2MoO6-RGO-TiO2 nanotube array ternary composite electrode.Compared with the TiO2 nanotube arrays,the absorption edge of the Bi2MoO6-RGO-TiO2 nanotube array electrode exhibited the significantly enhanced visible light absorption,and the photoluminescence spectral intensity and charge transfer resistance were lower.The hydrogen production rate of Bi2MoO6-RGO-TiO2 nanotube array electrode was 5.05 times that of the TiO2 nanotube arrays.3.In2O3 nanoparticles were synthesized by solvothermal method.Ag-TiO2 nanotube arrays binary composite electrode were prepared by pulse electrodeposition.The as-prepared In2O3 nanoparticles were then deposited on Ag-TiO2 nanotube arrays by ultrasonic electrophoresis,and In2O3-Ag-TiO2 nanotube array ternary composite electrode were obtained.Compared with the TiO2 nanotube array,the In2O3-Ag-TiO2 nanotube array electrode displayed red shifts in the bandgap transition and enhanced absorption in the visible light region.The photoluminescence spectrum test showed that the ternary composite structure efficiently promoted the separation of the photogenerated carriers.The produced hydrogen rate of In2O3-Ag-TiO2 nanotube array electrode was 5.32 times that of TiO2 nanotube array. |
