Construction Of Nickel Base Modified Mn_0.25Cd_0.75S Composite Catalyst And Its Photocatalytic Performance For Hydrogen Production

With the continuous development of industry,production and life,more and more fossil energy is exploited to meet our energy demand.Fossil energy is mainly composed of carbon and hydrogen.When it is burned in large quantities,it will also release some gases harmful to the environment and bring environmental pollution problems.Hydrogen energy is a new,green and renewable energy source.Its combustion calorific value is higher than that of traditional fossil energy,and the combustion product is water,which does not pollute the environment and is an environmentally friendly green energy.Under the irradiation of visible light,hydrogen can be obtained through the process of hydrogen production by semiconductor decomposition of water,thus realizing the utilization of hydrogen energy.More and more people pay attention to the development and exploration of efficient,stable and low-cost photocatalyst.Mn_0.25Cd_0.75S is a kind of solid solution photocatalyst material,which has suitable energy band position and band gap width and shows good visible light response.However,the high recombination rate of pure Mn_0.25Cd_0.75S photogenerated electrons and holes limits its further development in photocatalytic hydrogen production.Nickel-based material is a kind of non-precious metal material with rich content and excellent performance in nature,which can be used as a cocatalyst for photocatalytic hydrogen production.Mn_0.25Cd_0.75S photocatalyst can be compounded with nickel-based materials to form composite materials to further improve the photocatalytic hydrogen production performance of Mn _0.25cd_0.75S.In this study,Mn_0.25Cd_0.75S polyhedral photocatalyst was used as the main material,and boride,sulfide and hydroxide of nickel metal were selected as cocatalysts respectively.Through the strategy of cocatalysts modification and heterojunction construction,more catalytic active sites were provided for photocatalytic reaction,and the transfer and separation of photogenerated charges were promoted.The specific work of this paper is as follows:（1）α-NiS nanoparticles were prepared by solvothermal method and supported on the surface of Mn_0.25Cd_0.75S polyhedral photocatalyst.α-NiS/Mn_0.25Cd_0.75S composite showed enhanced photocatalytic hydrogen production performance,and the photocatalytic effect ofα-NiS/Mn_0.25Cd_0.75S composite loaded with 5wt%was the best,and its hydrogen production rate was 8.44 mmol/g/h g/h.Under the irradiation of visible light,the photogenerated electrons on the conduction band of Mn_0.25Cd_0.75S can be transferred toα-NiS nanoparticles,and the electrons gathered onα-NiS nanoparticles can reduce H⁺in water to produce hydrogen.α-NiS nanoparticles are smaller in size,which can provide larger specific surface area and more catalytic active centers for photocatalytic reaction.（2）Mn_0.25Cd_0.75S polyhedral photocatalyst was prepared by hydrothermal method,and a series of NiB/Mn_0.25Cd_0.75S composite materials were synthesized by loading NiB as cocatalyst on its surface.The results show that NiB/Mn_0.25Cd_0.75S loaded with 10%mass fraction shows the best photocatalytic hydrogen production performance under visible light irradiation,and its hydrogen production rate is 13.06 mmol/g/h,which is 3.7 times that of pure Mn_0.25Cd_0.75S.The interface contact between NiB and Mn_0.25Cd_0.75S is beneficial to the transfer of electrons from Mn_0.25Cd_0.75S to NiB,thus promoting the separation and transport of photogenerated electrons and holes.At the same time,NiB can also provide more active sites for the reaction,which is beneficial to the photocatalytic hydrogen production reaction.（3）Three-dimensionalβ-Ni(OH2) flower ball was synthesized by hydrothermal method,and it was compounded with Mn_0.25Cd_0.75S polyhedron to formβ-Ni（OH）₂/Mn_0.25Cd_0.75S composite.Among them,β-Ni（OH）₂/Mn_0.25Cd_0.75S composite loaded with 5wt%has the best photocatalytic effect,and its hydrogen production rate is 9.2 mmol/g/h.Its enhanced photocatalytic hydrogen production performance can be attributed to the construction of type Ⅱ heterojunction betweenβ-Ni（OH）₂ and Mn_0.25Cd_0.75S Heterojunction structure can reduce the rapid recombination of photogenerated electrons and holes at the interface,promote the separation and transmission of carriers,and further promote the photocatalytic hydrogen production reaction.