| With the development of economy,the demand for energy is getting larger and larger in various countries.Hydrogen will be an infinitely recyclable energy if photocatalytic hydrogen production process can be achieved.Semiconductor photocatalyst material has great prospects in this area.Hematite as a semiconductor material with the highest photoelectric conversion efficiency up to 15.5%,however,due to its shortcomings,such as short distance of photoelectron's migration,high rate of photoelectron-hole's recombination and higher hydrogen potential,the photoelectric conversion efficiency is far from the expected purpose.On this base,scientists have conducted extensive exploration experiment to improve its photoelectric properties by different way.In this dissertation,?-Fe2O3 nanorod arrays were deposited on FTO conductive glass substrates by hydrothermal-annealing method,iron source is FeCl3·6H2O.?-Fe2O3/rGO/Au was prepared by spin-coating-annealing and electrochemical deposition.The effects of surface modification methods such as Sn doping,acid treatment,and secondary hydrothermal treatment on the photoelectric properties of the material were investigated by scanning electron microscopy,X-ray diffraction,linear sweep voltammetry and electrochemical impedance spectroscopy.The main research contents and results are as follows:1.The?-Fe2O3 nanorod arrays were deposited on the FTO conductive glass substrate by a hydrothermal-annealing method.Graphite oxide was prepared by Hummers'way,which was purified by centrifugation and freeze-dried to obtain graphene oxide.The?-Fe2O3/rGO was prepared by spin-coating thermal reducation method.The reduction temperature and the spin-coating times of GO were studied by scanning electron microscopy,X-ray diffraction,linear sweep voltammetry and electrochemical impedance spectroscopy.The research results show that:?-Fe2O3 nanorod arrays have been successfully deposited on FTO conductive glass substrates,the length of the nanorod arrays was about 550 nm,the width was about 70 nm and the maximum photocurrent density was 0.05269 m A/cm2.By spin-coating the rGO material?three times,450°C?,the best photocurrent density is 0.2829 mA/cm2,at 1.23 V vs RHE,which is 5.4 times of the maximum photocurrent density of?-Fe2O3 nanorod arrays.2.HAuCl4 is the gold source,?-Fe2O3/rGO/Au composite system were prepared by electrochemical deposition.The influence of nucleation voltage,deposition voltage and deposition time on the photoelectric performance of?-Fe2O3/rGO/Au were researched by scanning electron microscopy,X-ray diffraction,linear sweep voltammetry and electro-chemical impedance spectroscopy.The research results show that:the optimal deposition scheme was:nucleated under 3 mmol/L HAuCl4,-1.4 V for 2 s;deposited under 1 mmol/L HAuCl4,-1.2 V for 25 s.At this time,the deposited nano-Au particles have a particle size of about 30-50 nm,the photocurrent density was improved 1.5 times up to 0.4192 mA/cm2,at1.23 V vs RHE.3.The Sn-doped?-Fe2O3 material was prepared by annealing at 800°C with tin tetrachloride as the tin dopant.The Sn-?-Fe2O3/rGO/Au system was prepared by surface modification with acid treatment and secondary hydrothermal treatment,the effects of acid treatment and secondary hydrothermal on the photoelectric properties of Sn-?-Fe2O3/rGO/Au were researched by scanning electron microscopy,X-ray diffractometry,linear sweep voltammetry,and impedance spectroscopy.The results show that:the?-Fe2O3 prepared by annealing at 800°C without SnCl4 is in the shape of a cylinder with a length of about 400 nm and a diameter of about 50 nm.At 1.23 V vs RHE,the photocurrent density can reach 0.2459m A/cm2,is 4.6 times that of the sample obtained by annealing at 550°C.After SnCl4 was added,the photocurrent density was nearly doubled,reaching 0.4856 mA/cm2.Then,after the acid treatment and the secondary hydrothermal surface modification,the photocurrent density further increased to reach 0.8742 mA/cm2 and 0.7707 mA/cm2,after coating the reduced graphene oxide material,the photoelectric property is improved again,the photocurrent density reaches 1.048 m A/cm2 and 0.9123 mA/cm2,after the deposition of the Au nanoparticles,the photoelectric properties are different with the degree of attenuation,the photocurrent density dropped to 0.7546 mA/cm2and 0.5624 mA/cm2. |
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