Construction Of Transition Metal Phosphides And Study On Photocatalytic Hydrogen Evolution Performance

Transition metal phosphides（TMPs）are considered as a kind of high-efficiency and long-term stable cocatalyst because of their low overpotential and fast kinetics of continuous hydrogen evolution（HER）.Separation and transfer of photoelectrons and holes is the most important process in photocatalytic reaction.At present,most of the reported photocatalysts have low photocatalytic hydrogen evolution performance due to the easy combination of electrons and holes,which limits the wide application of photocatalysis.Therefore,in order to improve the photocatalytic performance,the introduction of cocatalyst is considered.However,the high cost and rarity of precious metals in traditional cocatalysts severely limit their large-scale use,so it is of great significance to find cocatalysts to replace precious metals.In the early stage,there have been a lot of reports on the research of metal oxides,hydroxides,sulfides and phosphides as substitutes for precious metals.Among them,transition metal phosphides show excellent electrical conductivity and are considered as efficient and stable hydrogen evolution promoters,such as Ni₂P,Co P,Fe P,Ni Co P and other transition metal phosphides.The main research contents of this paper are as follows:（1）By improving the impregnation method,a new method for preparing Ni₂P/Cd S was developed.Spherical Ni₂P was grown on the surface of Cd S nanorods in situ.The research shows that Ni₂P/Cd S photocatalytic system can effectively separate and transfer photo-generated electrons and efficiently evolve hydrogen under visible light.As a cocatalyst,Ni₂P facilitates the transfer and separation of electrons and holes,provides more catalytic active sites for the generation of H₂,which can greatly improve the photocatalytic activity of Ni₂P/Cd S.When Ni₂P content is 3%,Ni₂P/Cd S has the highest photocatalytic activity for hydrogen production under visible light,with a surprising hydrogen production rate of 16.02 mmol h^-1g^-1,while Cd S is only 0.28mmol h^-1g^-1,which is 57 times of that of Cd S.It has excellent hydrogen evolution stability in four cycles.（2）g-C₃N₄ was modified by Co P,and Co P/g-C₃N₄ with excellent photocatalytic performance was successfully synthesized.g-C₃N₄ with large surface area will be in precise contact with Co P,which can effectively promote the transfer of electrons and effectively improve the photocatalytic performance of g-C₃N₄.When the content of Co P is 5%,under visible light,the photocatalytic activity of Co P/g-C₃N₄ is the highest,and the hydrogen yield is 375μmol h^-1g^-1,while that of g-C₃N₄ is only 35μmol h^-1g^-1,which is 10.7 times that of g-C₃N₄,and it has excellent hydrogen evolution stability in four cycle tests.（3）The heterojunction structure of g-C₃N₄/Cd S was modified by Ni Co P,and the photocatalyst Ni Co P-g-C₃N₄/Cd S was successfully designed and prepared,which can effectively separate and transfer photo-generated electrons and efficiently evolve hydrogen under visible light.In addition,Ni Co P-g-C₃N₄/Cd S photocatalyst has abundant surface active sites,and its photocatalytic hydrogen evolution performance is greatly improved.When the content of Ni Co P is 5%,the catalytic activity is the highest,and the hydrogen yield is 55.63 mmol h^-1g^-1,which is 23.35 times that of Cd S(2.38 mmol h^-1g^-1)and 11.51 times that of g-C₃N₄/Cd S(4.84 mmol h^-1g^-1).In addition,Ni Co P-g-C₃N₄/Cd S photocatalyst has good hydrogen production stability.The materials were characterized and analyzed by XRD,SEM,TEM,XPS,UV-Vis DRS,FTIR,UPS,N₂ adsorption-desorption process and electrochemical test.Figure[39]Table[6]Reference[131]...