Performance Research Of Transition Metal Sulfide Modified Carbon Nanofiber Photocatalyst Composites

With the increasing consumption of fossil energy in the modern world,people pay great attention to energy security and environmental protection.Efficient solar photocatalytic hydrogen production（H₂）technology is considered to be a promising strategy to solve this kind of energy challenge.However,rapid charge recombination,lack of active sites and unsatisfactory electron/hole trapping usually hinder the photocatalytic activity of hydrogen evolution in the process of water photodegradation.Zinc indium sulfide（Zn In₂S₄）and cadmium indium sulfide（Cd In₂S₄）are promising photocatalysts due to their excellent visible light capture ability,photostability and suitable band gap.However,due to its physical and structural defects,the photocatalytic activity of single-phase Zn In₂S₄or Cd In₂S₄catalyst is usually seriously degraded during hydrogen evolution.In order to optimize the carrier separation efficiency,an effective strategy is to modify one-dimensional（1D）carbon nanofibers（CNF）by coupling photocatalyst with cocatalyst（such as transition metal disulfide）.Transition metal sulfides,especially p-type layered molybdenum disulfide（Mo S₂）and layered tungsten disulfide（WS₂）,are particularly attractive.In this paper,carbon nanofiber supported heterojunction photocatalysis system materials were constructed by in-situ spinning chemical vapor deposition and hydrothermal treatment,which can not only provide sufficient substrate surface for the growth of single-phase Zn In₂S₄or Cd In₂S₄catalyst,but also provide abundant charge transfer channels and unsaturated photocatalysis sites.The main research contents are as follows:1.CNFs/Mo S₂/Zn In₂S₄layered three-dimensional composites with p-n heterojunction between two-dimensional（2D）phase planes were prepared by hydrothermal reaction.The effect of different content of Mo S₂on the hydrogen production performance of the catalyst was investigated.It is found that the 2D-2D interface between n-type Zn In₂S₄and p-type Mo S₂supported by CNFs has obvious rectifying effect,which is beneficial to the separation of interface charges and suppression of recombination of photogenerated electrons and holes.The large surface area of sulfide provides abundant sulfur rich active sites for hydrogen production.Under simulated solar irradiation,CNFs/Mo S₂/Zn In₂S₄composites loaded with 5 mmol Mo S₂showed good hydrogen evolution performance.The photocatalytic hydrogen production rate was above 151.42 mmo L·h^-1·g^-1,and the apparent quantum efficiency at 365 nm was 20.88%,which was 4.65 times that of Zn In₂S₄.2.Based on former experiments,using low-cost and simple electrospinning combined with etching technology,（porous）CNFs/WS₂nanofiber framework was prepared,and then porous CNFs/WS₂/Cd In₂S₄layered three-dimensional composite with heterojunction was prepared by hydrothermal reaction.The effect of different content of WS₂on hydrogen production performance of the catalyst was investigated.At the same time,the mechanism of carbon nanofiber in heterojunction is also analyzed.Compared with pure Cd In₂S₄,the porous CNFs/WS₂/Cd In₂S₄composite photocatalyst has the following obvious advantages:（1）high conductivity carbon fiber network enhances the conductivity of the electrode,which is conducive to electron transfer;（2）large specific surface area and porous carbon fiber skeleton can provide sufficient reaction space for photocatalytic hydrogen evolution;（3）the sacrificial agent can be adsorbed into the pores of carbon fiber to accelerate the capture of photogenerated holes.Therefore,the porous composite shows high photocatalytic efficiency.