Preparation Of Metal Sulfide Nanomaterials Loaded Tungstate And Its Photocatalytic Performance For Hydrogen Production

At present,human beings are facing the serious problem of resource shortage and pollution.The technology of photocatalytic decomposition of water to hydrogen can transform the pollution-free solar energy into a green source with H2 as the carrier,so it can overcome these problems more efficiently.Among all kinds of photocatalysts,the preparation and application of metal sulfides have been paid more and more attention by photocatalysis scholars because of their advantages such as wide absorption region and high utilization of visible light.Among them,how to solve the shortcomings of fast recombination of photogenerated carriers and strong photocorrosion in metal sulfide-based photocatalysts,so as to obtain metal sulphide-based photocatalysts with good hydrogen production performance and stability is always our concern.Therefore,in this paper,a series of metal sulfide-based photocatalysts containing tungstate were designed and prepared by compounding tungstate with metal sulfide.On this basis,the behavior of photocatalytic hydrogen production and its influencing factors were studied systematically.Finally,the photocatalytic hydrogen production mechanism of the above catalysts was further studied.The main research contents and achievements are as follows:Firstly,porous ZnWO4 nanoparticles were prepared using sodium phosphomolybdate as template by mechanical ball milling and high temperature calcination.Subsequently,the flower-like microspheres composed of ZnIn2S4 nano-particles embedded with ZnWO4 porous nanoparticles were prepared by hydrothermal method.On this basis,the photocatalytic hydrogen production behavior of the obtained samples was discussed in detail.Through the study,it was found that the photocatalytic system had excellent photocatalytic hydrogen production performance under the irradiation of visible light irradiation.Under the optimum conditions,the photocatalytic hydrogen production rate reached 8857.5 μmol g-1 h-1.More interestingly,as a cocatalyst,ZnWO4 porous nanoparticles have better performance than solid ZnWO4 nanoparticles.When ZnWO4 porous nanoparticles are used as the cocatalyst,the hydrogen production rate is 2.15 times higher than when ZnWO4 solid nanoparticles are used as the cocatalyst.The study of its photocatalytic hydrogen production mechanism shows that the electron transfer in the catalytic system may follow the Z-scheme electron transfer mechanism.Its excellent photocatalytic hydrogen production performance should be attributed to the effective separation of photogenerated carriers.These results will provide new ideas for further improving the photocatalytic activity of ZnIn2S4-based photocatalysts.Second,SrWO4/CdS composite nanoparticles were prepared by hydrothermal method using CdS nano-materials prepared by coprecipitation as starting materials.At the same time,the photocatalytic activity of the system was investigated.The results show that the introduction of SrWO4 can significantly improve the photocatalytic performance of CdS.On SrWO4/CdS nanoparticles,the fastest precipitation rate of H2 is 392.5 μmol g-1 h-1,5.8 times that of pure CdS nanoparticles.More interestingly,SrWO4/CdS nanoparticles have good stability.After 10 times of use,the hydrogen evolution rate on the photocatalyst can still reach 473 μmol g-1 h-1.This is the same as the photocatalytic activity of the sample used once,and even 37%higher than that of the sample not used.In contrast,the photocatalytic activity of pure CdS nanomaterials is only 57%of that of unused samples after 5 times of use.In this photocatalysis system,SrWO4 acts as both reduction and oxidation cocatalyst,which can significantly enhance the photocatalytic hydrogen production activity and stability of CdS at the same time.The reason may be the formation of S-Scheme heterojunction at the interface of SrWO4 and CdS.Under its action,photogenerated carriers are separated efficiently,and the photoetching of CdS is also effectively inhibited.Thirdly,on the basis of SrWO4/CdS composite nanomaterials,we constructed a photocatalytic hydrogen production system containing SrF2,SrWO4 and CdS by hydrothermal method to further improve the photocatalytic activity of CdS.At the same time,the photocatalytic hydrogen production behavior of the obtained samples was discussed in detail.The results show that the photocatalyst has excellent photocatalytic performance for hydrogen production.Under the optimum hydrogen production conditions,the hydrogen production rate can reach 1987.5 μmol g-1 h-1.In addition,the constructed photocatalytic system also has good stability.In the cycle hydrogen production experiment,its photocatalytic hydrogen production activity in the sixth cycle is basically consistent with the initial photocatalytic activity.