Study On Design And Performance Of ZnS-ZnO Heterostructures For Photocatalytic Pure Water Splitting

As a green and healthy emerging technology,photocatalysis is considered as a potentially effective clean energy conversion technology.Metal oxides and sulfide semiconductor photocatalytic materials are widely used in the field of photocatalytic decomposition of water to produce hydrogen due to their advantages of low cost,easy preparation and strong photoredox and reduction capacity.However,due to the metal oxides and sulfides in the photocatalytic decomposition of water reaction process,it is easy to occur photocorrosion.For example,in order to inhibit photocorrosion and improve the stability of photocatalytic hydrogen production,ZnO and ZnS added sacrificial agent into the reaction system in the photocatalytic hydrogen production by water decomposition.However,the addition of sacrificial agent not only increases the operating cost,but also inhibits the generation of oxygen in the reaction system,which is unfavorable to the application of photocatalytic technology.Therefore,it is of great significance to study the photocatalytic decomposition of pure water with efficient and stable heterogeneous structures.A novel ZnS-ZnO heterostructure photocatalytic hydrogen production material was constructed by morphology and structure regulation,surface and interface structure modification and cocatalyst optimization.The photocatalytic decomposition of pure water by stoichiometric ratio of hydrogen to oxygen was finally achieved.Firstly,ZnO nanosheet were obtained by ph regulation.ZnO nanosheets were vulcanized to form ZnS layer by ion exchange.ZnS-ZnO sheet heterogeneous photocatalytic materials were obtained.The ZnS-ZnO heterostructure retains the morphology of nanosheet,which is conducive to shortening the photogenic electron-hole migration distance,reducing the recombination rate,and effectively increasing the reactivity site.Compared with the pure ZnO and ZnS,the ZnS-ZnO heterostructure exhibited good hydrogen-producing performance in photocatalytic decomposition of pure water.The heterostructure of ZnS-ZnO showed the photocatalytic decomposition of pure water to produce hydrogen and oxygen simultaneously by supporting the load of Pt nanoparticles.A series of electron paramagnetic resonance(ESR)spectra were used to demonstrate that the transport mechanism of Z-Scheme carrier in ZnS-ZnO was successfully realized.In order to solve the problem that ZnS-ZnO cannot achieve stoichiometric ratio in photocatalytic decomposition of hydrogen and oxygen production in water,we further optimized and improved the interface and surface atomic states of ZnS and ZnO.ZnO nanosphere with diameter less than 25 nm was synthesized by solvent heat method using ethylene glycol as solvent.Then,using thioacetamide as the sulfur source,ZnO nanosphere was vulcanized by ion exchange method at constant temperature to obtain ZnS@ZnO core-shell heterostructure spherical photocatalytic material.In order to improve the stability of pure water decomposition of ZnS@ZnO heterostructure photocatalytic material,the atomic structures on the interface and surface of the heterostructure spheres were strengthened by high-temperature calcining.After heat treatment,ZnS@ZnO heterogeneous structure ball showed good stability.After being supported with Rh as a co-catalyst,Rh/ZnS@ZnO core-shell heterostructure sphere achieved sustained and stable photocatalytic decomposition of pure water to produce hydrogen and oxygen by stoichiometric ratio,and the photocatalytic decomposition efficiency was also significantly improved.Finally,ZnS@ZnO heterostructure with different cocatalysts for photocatalytic full water splitting were investigated.The effects of Au,Pt,Rh,RuO2 and their combination on the full water decomposition performance of ZnS@ZnO heterostructure were studied.