Study On Preparation And Photocatalytic Hydrogen Production Performance Of G-C₃N₄/MoS₂ Composite Materials

Hydrogen energy,as an ideal energy source,has the characteristics of high energy density,zero carbon emission and renewable energy.It has been attracted wide attention.Photocatalytic decomposition of water for hydrogen production is a green technology with broad application prospects.In recent years,graphitic carbon nitride（g-C₃N₄）has attracted much attention in the field of photocatalysis due to its advantages of high stability,excellent photoelectric properties and easy large-scale preparation.However,the photocatalytic activity of g-C₃N₄ is limited due to its bulk structure,low light absorption capacity and high photogenerated electron-hole pair recombination rate.In this paper,g-C₃N₄ as the research object,its photocatalytic hydrogen production activity was greatly improved by controlling the morphology of g-C₃N₄ and co-catalyst molybdenum sulfide composite.In addition,the mechanism was further analyzed.The brief contents are the following:The porous graphitic carbon nitride was prepared by a co-thermal polymerization method.The mass ratio effects of precursor melamine to urea on the morphology,specific surface area,light absorption,electron-hole recombination and hydrogen production of carbon nitride were investigated.When the mass ratio was1:3,the prepared photocatalyst g-C₃N₄ showed a thin lamellar structure with a specific surface area of 72.2 cm²/g and the lowest carrier transport resistance.And the hydrogen production of this carbon nitride was the highest,about 1.173mmol·g^-1·h^-1.Finally,the cyclic experiment was conducted to prove that this porous graphitic carbon nitride had good stability.In order to improve the performance of photocatalytic hydrogen production,molybdenum disulfide（MoS₂）was selected as a co-catalyst and porous g-C₃N₄/MoS₂heterojunctions were synthesized by the solvothermal method.The structure of g-C₃N₄/MoS₂ was characterized by XRD,and the morphology,specific surface area,chemical composition,light absorption,electron-hole recombination and carrier transport of g-C₃N₄/MoS₂ were analyzed by SEM,BET,FT-IR,UV-vis,PL and EIS.The effects of different molar ratios,reaction temperature and solvents of heterojunctions on the photocatalytic performance were studied.It was found that the hydrogen production rate of g-C₃N₄/MoS₂ was 2385.491μmol·g^-1·h^-1 when the molar ratio of porous graphitic carbon nitride to molybdenum disulfide was 5:1under the conditions of 200℃as well as 2:3 mixed solvents of DMF and absolute alcohol.It is 237 times higher than the performance of single porous graphite carbon nitride(10.044μmol·g^-1·h^-1).Finally,the hydrogen production mechanism of porous g-C₃N₄/MoS₂ heterojunction was investigated.