Preparation And Photocatalytic Performance Of NiCo₂O₄/g-C₃N₄ Heterojunction Composite

The energy crisis and environmental issues have become the primary challenges facing our current social development.Solar energy has the advantages of renewable and clean energy,and hydrogen energy,as an emerging clean energy,has the characteristics of high efficiency and pollution-free.Photocatalytic water splitting to produce H₂ can convert solar energy into hydrogen energy after some chemical processes.It is currently known as a simple,low-energy and pollution-free hydrogen production method.Among them,the design and construction of composite materials with the advantages of low cost,high catalytic ability,good physical and chemical stability and environmentally friendly is an important step that can use solar energy to apply photocatalytic H₂ production technology to practical production.The g-C₃N₄ material has been extensively studied in the field of photocatalysis because of its simple preparation process,low equipment requirements,suitable band gap and unique graphene-like two-dimensional layered structure.However,the narrow absorption range of visible light and the high charge recombination rate seriously hinder the possible application of g-C₃N₄ in the fields of energy and environment.NiCo₂O₄ is a binary metal oxide with a spinel structure,which has the advantages of low price,environmental friendliness,good electrical conductivity,and rich redox reactions,and can be used as a modifier of g-C₃N₄.Therefore,this paper combines the design and construction of materials with the characterization analysis to improve the photocatalytic hydrogen evolution ability of the NiCo₂O₄/g-C₃N₄composites from the aspects of morphology control,adding co-catalyst,and building heterostructure,and explore its possible photocatalytic reaction mechanism.The main research contents are as follows:1.Using urea as the precursor,g-C₃N₄ nanosheets were obtained through two calcinations processes.NiCo₂O₄ materials were prepared by hydrothermal method using Co Cl₂ and Ni Cl₂as cobalt and nickel sources.The NiCo₂O₄/g-C₃N₄ heterojunction composite material was obtained by the method of mixing and calcination.The construction of the heterojunction between the two materials improves the absorption capacity of visible light,facilitates the separation and transfer of carriers,and thus improves its photocatalytic ability to generate H₂.This experiment can provide a valuable reference for the preparation of high-efficiency heterojunction photocatalysts.2.The electrochemical workstation was used to evaluate the photoelectric performance of the NiCo₂O₄/g-C₃N₄ composite material,which showed that CN-5%has higher photocurrent and smaller transfer resistance.The gas chromatograph was used to perform photocatalytic hydrogen evolution experiments on NiCo₂O₄/g-C₃N₄ photocatalyst.The results showed that compared with the original g-C₃N₄,the NiCo₂O₄/g-C₃N₄ has higher hydrogen production activity,indicating that the composite NiCo₂O₄ facilitates the separation and migration of carriers and improves the utilization of light energy.When the loading of NiCo₂O₄ is 5%,the H₂ production rate of CN-5%can reach 1041.9μmol g^-1 h^-1.After passing the 9-hour cycle test,the total amount of H₂ produced by CN-5%did not decrease significantly,showing excellent stability.The results showed that the 5%-NiCo₂O₄/g-C₃N₄ heterojunction composite material synthesized in this study has excellent performance of photocatalytic water splitting to produce hydrogen and maintains good stability,which has a great development space in the field of photocatalytic H₂ production.