Preparation Of Semiconductor Materials Coupled With WS₂ And Their Photocatalytic Water Splitting Properties

With the development of human society,energy and environment have become the important foundation for people to survive and develop,as well as the guarantee of human engage in all production activities.However,in recent decades,with the increase of world population and the rapid development of social economy,the demand for natural resources is increasing and fossil energy faces enormous crisis.Consequently,environment pollution issue has become more and more serious,and has even threat to human survival and sustainable development.Therefore,it is urgent to solve the problem of energy shortage and environmental pollution.As a clean,efficient and reproduced energy,solar energy has been considered as one of the major content for sustainable development strategy.Photocatalytic water splitting to produce hydrogen will be a best way to solar energy conversion and utilization.In this dissertation,we prepared a series of composite catalyst,using WS₂ as a co-catalyst.The structure and photoelectrochemical characterization of the composites were carried out.The photocatalytic activity and reaction mechanism of the composites were also investigated in semiconductor photocatalytic system and photoelectrochemical cell system.The main points were shown as follows:?1?A novel noble metal-free photocatalyst consisted with WS₂ and TiSi₂ using for water splitting under visible light irradiation has been successfully prepared.The obtained samples were characterized by X-ray diffraction?XRD?,scanning electron microscopy?SEM?,X-ray photoelectron spectroscopy?XPS?,UV-vis diffuse reflectance absorption spectra?DRS?and photoelectrochemical measurements.The results demonstrate that WS₂and TiSi₂ have been effectively combined and then speeded up the photogenerated charges transfer and separation.Under 6 h visible light??>420 nm?irradiation,the optimal?TiSi₂/WS₂-1?catalyst produced the highest hydrogen evolution amount of 580.69?mol·g^-1,which is much higher than that of pure TiSi₂(416.01?mol·g^-1)and TiSi₂/Pt-1(540.85?mol·g^-1),respectively,under the same conditions.Last we investigated the proposed mechanism of the photocatalytic reaction.?2?Zn doped hematite??-Fe₂O₃?Zn??nanorods were synthesized by a facile hydrothermal method.The structure and photoelectrochemical performance of p-type Zn doped hematite was characterized by X-ray diffraction?XRD?,transmission electron microscopy?TEM?,X-ray photoelectron spectroscopy?XPS?,UV-vis diffuse reflectance absorption spectra?DRS?and photoelectrochemical measurements.The negative slope in the Mott-Schottky plot proved the p-type conduction of Zn-doped?-Fe₂O₃.By modifying hematite with WS₂,the photoelectrochemical performance of hematite can be further enhanced.The as-prepared p-type?-Fe₂O₃?Zn?/WS₂ photocathode and Pt electrode were used to assemble a photoelectrochemical tandem cell.The self-assembled device had been successfully demonstrated to split water into O₂ and H₂ driven by UV-vis light.The optimal Zn doping concentration was found to be 3%.This study suggests a promising method for constructing an efficient photoelectrochemical tandem device for light driven total water splitting.At last,we investigated the separation and transfer process of photogenerated electrons.?3?p-type Zn doped hematite??-Fe₂O₃?Zn??photocathode and n-type hematite photoanode were prepared by a facile hydrothermal method,modified by WS₂ and then assembled into a photoelectrochemical tandem cell.The two electrodes were characterized by X-ray diffraction?XRD?,transmission electron microscopy?TEM?,X-ray photoelectron spectroscopy?XPS?,UV-vis diffuse reflectance absorption spectra?DRS?and photoelectrochemical measurements.Under the irriadiation of UV-vis light,the photoelectrochemical tandem cell showed the excellent photocatalyitic avtivity for water splitting.The optimal loading content of WS₂ was found to be 2%.At the moment,the amount of H₂ and O₂ was 12.86?mol and 4.39?mol,respectively.At last,we discussed the separation and transfer process of the photoelectrons and proposed reaction mechanism.