Photocatalytic Activity Of Ti₃C₂ MXene Modified Metal Sulfide With Efficient Visible Light For Hydrogen Production

With the depletion of fossil energy,the intensification of greenhouse effect and frequent climate disasters caused by industrial development,the development of new energy becomes an urgent matter.Hydrogen energy is a clean and renewable fuel.Due to its advantages of high calorific value and no by-products in combustion,hydrogen is considered as a potential energy source to improve environmental problems and solve energy crisis.At present,photocatalytic decomposition of water to produce hydrogen is considered as an ideal strategy for solar energy storage and conversion.Among semiconductor photocatalysts,ZnIn₂S₄and CdS with various morphological structures have become a research hotspot due to their excellent visible light absorption performance,suitable band gap and low cost.However,due to the limited absorption range of visible light and the fast recombination rate of photoinduced electrons and holes,the photocatalytic performance of single ZnIn₂S₄and CdS is not satisfactory.In recent years,a new class of graphene-like ultra-thin Ti₃C₂MXene materials have emerged as cocatalysts in the field of photocatalysis due to their excellent electrical conductivity,good hydrophilicity,abundant surface functional groups and large specific surface area.However,due to the instability of Ti₃C₂in aqueous solution and air,and the tedious process of preparing ultra-thin Ti₃C₂matrix composites,it is very likely to cause oxidation of Ti₃C₂,leading to its inactivation.Therefore,this paper aims to improve the above problems,and the specific research content is as follows:Firstly,ZnIn₂S₄flower spheres were grown in situ between multilayer Ti₃C₂MXene layers by solvothermal method,and ultra-thin Ti₃C₂nanosheets/ZnIn₂S₄micro-flower spheres binary composites were obtained.Compared with the preparation of conventional ultra-thin Ti₃C₂-based composite,the Ti₃C₂MXene blocks can be separated and layered simultaneously in this work.The obtained ZnIn₂S₄/Ti₃C₂binary composite was applied to the photocatalytic production of hydrogen with node-assisted visible light drive.The decomposition efficiency of the optimized sample was 978.7μmol·h^-1·g^-1,and the apparent quantum efficiency at 420 nm was 24.2%,2.7 times higher than that of pure ZnIn₂S₄.Based on the comprehensive analysis of spectral measurement,electrochemical technique and band theory,it is explained that the enhancement is mainly due to（1）the highly exposed surface is conducive to the full exposure of the reaction site.（2）The close contact interface is favorable for photogenic carrier transfer.This study provides a new strategy for the development of competitive ultra-thin Ti₃C₂MXene based composite photocatalysts and noble metal free photocatalysts.Secondly,a kind of CdS-Ti₃C₂/MoS₂ternary nanocomposite with sandwich lamellar structure was constructed by microwave hydrothermal method.Due to the strong reducing property of Ti vacancy on the ultrathin Ti₃C₂surface,MoS₂nanoparticles（20-50 nm）can grow in situ on the ultrathin Ti₃C₂surface at room temperature to form a close interfacial contact Ti₃C₂/MoS₂.Furthermore,CdS was covered on Ti₃C₂/MoS₂surface by microwave hydrothermal method.Ultra-thin Ti₃C₂has a two-dimensional layered structure,which can be used as a support carrier to avoid the agglomeration of CdS particles and provide a large number of suitable active sites for hydrogen production.Moreover,the synergistic effect between Ti₃C₂and MoS₂further provides an efficient charge separation channel for photogenerated electrons from CdS.Therefore,under visible light irradiation,the H₂generation rate of CdS-Ti₃C₂/MoS₂reaches 14.88 mmol·h^-1·g^-1,which is 6.8 times and 2.8times of pure CdS and CdS/Ti₃C₂,respectively.The results provide useful insights for simplifying the preparation process and developing photocatalysts with novel nanostructures.