Preparation And Photoelectrochemical Property Of Nano SnS/SnS₂ Heterojunction

With the development of industry and the progress of science and technology,environmental problems and resource crisis are increasingly serious.Solar energy has been widely studied as a sustainable resource and a clean energy source.Solar photocatalysis technology is a very promising approach to solve environmental and resource problems.As a photocatalyst,TiO₂ has been widely studied and applied since it was discovered.However,due to the wide band gap of TiO₂,it can only absorb less than 5% of solar energy and has a low utilization efficiency of solar energy.In recent years,sulfides have been used as alternative material for visible solar photocatalysis due to their special two-dimensional structure and suitable band gap.SnS₂ has visible light response,and it is non-toxic and chemically stable,so it is a promising visible light catalytic material.However,due to the poor mobility and high recombination rate of photo-generated carriers,SnS₂ is easy to be deactivated.SnS is a narrow gap semiconductor,which responds in the near infrared region and has high charge mobility as well as light absorption coefficient.At present,in order to improve the photocatalytic performance of SnS₂,the loaded precious metals and heterojunction materials are mainly used.In this paper,Snnanoparticles were firstly prepared by dc arc plasma technology,and then Snnanoparticles and sublimated sulfur were used as precursors.The bulk SnS,SnS₂ and SnS/SnS₂ heterojunction nanosheets were synthesized by in-situ one-step sulfurization method.XRD,Raman and XPS were used to analyze the phase and the chemical composition of samples.The morphology of the sample was characterized by SEM and TEM,and the basic photoelectric characteristics of samples were determined by UV-Vis spectrophotometer.The photoelectrochemical property of SnS/SnS₂ heterojunction were studied by a three-electrode test system with Xenon lamp as the simulated light source.In the study,it was found that the samples could be transformed between SnS and SnS₂ by controlling the synthesis conditions during the sulfurization process due to the different formation energies of tin sulfides.The change of tin sulfur mole ratio and calcination temperature could affect the change of SnS and SnS₂ contents in the SnS/SnS₂ heterojunction nanosheets.Compared with pure SnS₂,the SnS/SnS₂ heterojunction nanosheets had a higher light absorbance.In addition,the photoelectrochemical properties of SnS/SnS₂ heterojunction nanosheets were significantly higher than pure SnS and SnS₂.This is because the SnS/SnS₂ heterojunction belonged to type I heterojunction,and the photo-generated carriers of SnS₂ all migrated to SnS.Due to the large band difference between the conduction band and valence band of SnS and SnS₂,the migration rates of electrons and holes are different,that is beneficial to reduce the recombination rate of photo-generated carriers.Morover,when the photo-generated carriers in the heterojunction transferred to SnS due to the higher electron mobility of SnS,they can quickly participate in the catalyst reaction on the particles’ surface,and then the recombination rate of photo-generated electrons and holes can be reduced.