Preparation And Photoelectrochemical Water Splitting Performance Of Zinc-based Sulfide Composite Materials

Due to the huge consumption of non-renewable energy and the increasingly serious environmental pollution problem,it is imperative to develop renewable energy neither reling on fossil fuels nor emiting carbon dioxide.Solar energy,as a sustainable and clean energy,is the source of everything people depend on for survival,and among the many energy conversion and utilization ways,the photoelectrochemical water splitting has been regarded as a promising artificial photosynthesis method using solar energy.At the same time,semiconductor catalytic materials play an important role in the efficient utilization and conversion of solar energy.The properties of multiphase photoelectrochemical water splitting mainly depend on the interfacial properties of the material.It is an effective method to construct heterogeneous junctions to optimize the interface engineering of materials.The energy band structure of the electrode has been improved by combining other materials to promote the charge transfer between different components.In this paper,a composite material for zinc-based sulfur compounds and tin compounds is designed,the photoelectrochemical water splitting properties of which are systematically explored,and the effects of morphology and interfacial heterogeneous structure on light capture and carrier transport are revealed.The main contents are as follows:(1)Three dimensional Au-SnS2/ZnS with hollow structure was prepared by the self-template method and hydrothermal method.The lamellar self-assembled SnS2/ZnS three-dimensional hollow structure was prepared by the self-template method and hydrothermal method.Composite materials with different morphologies have been obtained by adjusting the ratio.Combined with SEM morphology characterization and XRD composition characterization analysis,the 3D hollow structure with the best ratio have been obtained,which is conducive to enhancing the light absorption capacity and improving the photoelectrochemical water splitting performance of the photoanode.5-15 nm Au nanoparticles were prepared by chloroauric acid reduction method.HRTEM,TEM analysis showed that the uniform composite of Au nanoparticles and SnS2/ZnS 3D hollow structure was achieved.The optical performance,carrier transport performance and photoelectric catalytic performance of Au-SnS2/ZnS and Au-SnS2 materials were compared and studied.Under the bias voltage of 1.23V(vs.RHE),the photocurrent density of Au-SnS2/ZnS of the photoelectrode material can reach 4 times that of SnS2,and 1.5 times that of SnS2/ZnS.The main reasons are as follows:the formation of heterostructure promotes the effective separation of electrons and holes,and the matching band structure effectively accelerates the transmission between photogenerated electrons and holes;the existence of the rich phase interface between SnS2 and ZnS shorted the transmission path and accelerated the carrier transmission.Plasma Au nanoparticles can be used as photosensitizers to absorb incident photons and inject high-energy carriers into the semiconductor in indirect contact with them.The results show that the hollow structure and the rich phase interface engineering play an important role in promoting the water decomposition performance of the materials.(2)The Cs2SnI6 modified MOF derivative,N doped C ZnSe(simply called ZnSe/NC),was prepared by coprecipitation-heat treatment and applied to photoelectrochemical decomposition of water for the first time.The relationship between its microstructure and its PEC performance is studied,the composite mode of the two is analyzed,and the performance of the two in different electrolytes is discussed.First,ZnSe of MOF derivative N doped C was obtained by selenization with ZIF-8 as the framework.The BET test showed that the product had a large specific surface area and could provide more active sites.Then the stable non-toxic tin-based perovskite material Cs2SnI6 was synthesized by simple solution method at low temperature.The product was more stable than the traditional perovskite material at room temperature and humidity.Through SEM,TEM.HRTEM and other technical characterization,it can be known that Cs2SnI6 is evenly distributed on ZnSe/NC surface.By regulating the load of Cs2SnI6 on ZnSe/NC,the correlation between the material components and their macroscopic morphology and performance was explored.The test results showed that the introduction of Cs2SnI6 could significantly enhance the light absorption performance of the photoelectrode material ZnSe/NC/Cs2SnI6(simply referred to as ZNCS).By studying the photochemical properties of the electrode material in different electrolytes,it is found that the electrode material has the best performance in the neutral electrolyte,which indicates that the electrode material is more stable in the neutral solution.This is due to the following reasons:First,the introduction of the narrow band gap Cs2Snl6 semiconductor broadened the light absorption range and improved the light absorption performance of the composite materials.Second,Type II heterojunction built up by ZnSe with direct band gap and Cs2SnI6,speeds up the light carrier separation and transfer.Third,the MOFs derivative ZnSe/NC inheriting the MOF framework,has a larger specific surface area,provides more active sites,and facilitates interfacial electron and hole transfer.The results show that the large specific surface area,porous structure and matching band structure of ZnSe/NC/Cs2SnI6 at nanoscale can effectively improve the photoelectrochemical water splitting performance.