Study On Construction And Hygrogen Evolution Performance Of Nickel Phosphide And Nickel Metaphosphate Co-catalyzed Semiconductor Composite Photocatalytic Materials

The development of visible-light-driven efficient,stable,and inexpensive photocatalysts for water-splitting hydrogen production is an important topic to address global energy and environmental challenges.At present,the introduction of cocatalysts into the photocatalytic water splitting system for hydrogen production to develop efficient composite photocatalytic materials has become a research hotspot.Non-precious metal phosphide cocatalysts have attracted much attention because of their low cost,stable structure,and simple preparation,which can effectively replace the functions of noble metals.In this paper,Cd S nanoparticles（NPs）,Cd S nanowires（NWs）and Cd_0.5Zn_0.5S nanoparticles are used as the main catalysts,respectively,and the non-precious metal nickel phosphide or nickel phosphide-phosphate binary composite material is used as the cocatalysts to improve the visible light absorption ability and promote the separation and migration of photogenerated electron-hole pairs by constructing binary or ternary composites.So as to improve the visible light decomposition of aquatic hydrogen production activity of photocatalytic materials.The main results are as follows:1.Preparation and performance study of Ni（PO₃）₂-Ni₂P/Cd S NPs:Combined with the construction of heterojunction and co-catalyst modification,Ni（PO₃）₂-Ni₂P binary co-catalyst was prepared by thermal phosphorylation of flower globular Ni（OH）₂as precursor.The Ni（PO₃）₂-Ni₂P binary cocatalyst was combined with Cd S NPs by means of ultrasonic chemical synthesis to form a ternary photocatalytic material.The composition ratios of the binary cocatalysts were adjusted,and the characterization tests were carried out by XRD,SEM,TEM,FTIR,XPS,EIS,UV-vis DRS,and PL spectroscopy.The photocatalytic hydrogen production rate of Ni（PO₃）₂-Ni₂P/Cd S NPs loaded with 8 wt%reaches 4237μmol·g^-1·h^-1,which is 19 times that of Cd S NPs(217μmol·g^-1·h^-1),and the hydrogen production rate is about 89%of the initial value after six catalytic cycles.The absorption edge of Ni（PO₃）₂-Ni₂P/Cd S NPs is obviously red-shifted,the band gap is reduced to 1.86 e V,and the overpotential of H⁺reduction is reduced.Through the synergistic effect between Ni（PO₃）₂-Ni₂P and Cd S NPs,the visible light absorption properties are enhanced and the separation and migration of photogenerated electron-hole pairs are promoted,thereby significantly improving the photocatalytic hydrogen production activity of Cd S NPs.2.Preparation and properties of Ni（PO₃）₂-Ni₂P/Cd S NWs:Ni（PO₃）₂-Ni₂P binary cocatalysts was prepared by thermal phosphorylation and sonochemical methods using flower globular Ni（OH）₂as precursor.Ni（PO₃）₂-Ni₂P/Cd S NWs ternary photocatalytic materials were prepared by solvothermal in-situ synthesis.The Ni（PO₃）₂-Ni₂P nanosheet arrays with lower Fermi energy and strong electron trapping ability promote the effective separation of electrons and holes on Cd S NWs,and enhance the photocatalytic hydrogen production activity.5wt%Ni（PO₃）₂-Ni₂P/Cd S NWs has a photocatalytic hydrogen production activity of 5093μmol·g^-1·h^-1,which is about 16times that of Cd S NWs.In the 18 h hydrogen production cycle experiment,the sample still remains good stability of the initial hydrogen production rate of 83%.3.Preparation and properties of Ni₂P/Cd_0.5Zn_0.5S composites:Cd_0.5Zn_0.5S nanoparticles and Ni₂P nanosheets were prepared by precipitation-hydrothermal method and low temperature thermal phosphating method,respectively,and Ni₂P/Cd_0.5Zn_0.5S binary composites were prepared by ultrasonic cavitation effect.The well-crystallized Ni₂P nanosheets are uniformly dispersed among the Cd_0.5Zn_0.5S nanoparticles,and the close contact between them effectively promotes the separation and transfer of photogenerated carriers.At the same time,the narrower band gap and the active sites provided by Ni₂P promote the photocatalytic hydrogen production from water,thus the photocatalytic activity and stability of hydrogen production are significantly improved.When the Ni₂P content is 10 wt%,the photocatalytic hydrogen production rate of the composite is as high as 19.133 mmol·g^-1·h^-1,which is about 2.4 times that of Cd_0.5Zn_0.5S(7.865 mmol·g^-1·h^-1),and the hydrogen production rate after seven photocatalytic cycling experiments still has 91% of the initial value.