Solution-phase Synthesis Of Transition Metal Selenide Co-catalysts For Photocatalytic Hydrogen Production Application

Semiconductor photocatalytic photocatalytic for hydrogen evolution from water splitting is a new energy technology that can effectively alleviate problems such as energy shortage and environmental pollution.The development of highly active and stable photocatalysts with visible light response is the core of research in this field.However,pure-phase semiconductor photocatalysts have fast photogenerated electron-hole pair complexation efficiency,which greatly limits their catalytic activity.The co-catalyst modification can effectively promote semiconductor photogenerated carrier separation and migration to improve the photocatalytic activity for hydrogen evolution from water splitting.Transition metal selenide is a cheap and efficient co-catalyst with great potential for application in the field of photocatalytic production hydrogen.In this paper,MoSe₂ and NiSe₂ were prepared by liquid-phase method,and then MoSe₂/g-C₃N₄and NiSe₂/CdS composites were constructed to investigate the photocatalytic hydrogen production performance of the samples,respectively.Finally,this paper reveals the mechanism of the role of transition metal selenides in the photocatalytic activity for hydrogen evolution from water splitting.The details of the study and the results are as follows:（1）MoSe₂/g-C₃N₄ nanocomposites prepared and photocatalytic hydrogen production performance research.Firstly,homogeneous molybdenum diselenide（MoSe₂）nanoparticles were prepared by the solvothermal method,and then loaded onto g-C₃N₄ nanosheets to prepare MoSe₂/g-C₃N₄ nanocomposites.Secondly,the photocatalytic hydrogen production rate of 7MS/CN under visible light was 287.3（？）mol·h^-1·g^-1 by optimizing the mass ratio of MoSe₂.Moreover,the hydrogen production rate of7MS/CN did not decrease significantly in the cyclic reaction test（17.5 h,5 cycles）,indicating that MoSe₂/g-C₃N₄ has a good stability.Finally,the photoluminescence（PL）spectroscopy,electrochemical hydrogen precipitation（HER）and photoelectrochemical（PEC）tests elucidated that the modification of MoSe₂nanoparticles facilitated the separation of photogenerated carriers and photogenerated charge transfer of g-C₃N₄,which significantly increased the photogenerated electron transfer rate and promoted the improvement of the photocatalytic activity for hydrogen evolution from water splitting.（2）NiSe₂/CdS nanocomposites synthesis and their photocatalytic hydrogen production performance research.Firstly,four different crystalline structures of NiSe₂ were prepared by liquid phase method at different reaction temperatures.Through TEM analysis,these four NiSe₂ have similar microscopic morphology.Tested by XRD and HRTEM,NiSe₂-180℃ was an orthorhombic crystalline phase structure,NiSe₂-240℃ was a mixed orthorhombic and cubic biphasic crystal structure,NiSe₂-280℃ was a cubic crystalline phase structure,and NiSe₂-300℃ sample was a mixed cubic NiSe₂ and hexagonal Ni_0.85Se crystalline phase structure.Secondly,NiSe₂/CdS composites were synthesized by in situ growth method,and then analyzed by photocatalytic hydrogen production performance,NiSe₂-240℃/CdS has better photocatalytic hydrogen production activity(3039（？）mol·h^-1·g^-1)than the other three composites,which is 6.5 times and 1.7 times higher than that of pure CdS(466（？）mol·h^-1·g^-1),3 wt%-Pt/CdS(1819（？）mol·h^-1·g^-1)and 6.5 and 1.7 times the hydrogen production rate,respectively.Finally,photoluminescence（PL）,electrochemical hydrogen precipitation（HER）and photoelectrochemical（PEC）tests were performed to clarify that the loaded co-catalyst NiSe₂ can effectively promote the separation and transfer of CdS photogenerated carriers and significantly improve photocatalytic activity for hydrogen evolution from water splitting.