Synthesis And Photocatalytic Properties Of Carbon/Ceria With Biological Structure

Energy shortage and environmental pollution are two important factors which limit economic development.Due to the dual pressure of reducing environmental and energy resources,the development and application of clean energy have received extensive attention.As a high-density energy source,hydrogen energy only generates water during the combustion process,which can effectively solve the problems of energy shortage and environmental pollution.Photocatalytic water-hydrogen production technology utilizes a semiconductor catalyst to decompose water into hydrogen under the drive of light,and the entire process does not cause pollution to the environment.It is one of the novel types of energy sources currently researched.In this paper,a biomimetic template method is used to synthesize carbon/ceria composites with specific biomimetic structures.The layered biomimetic carbon formed after the organisms are calcined at high temperature is retained in the synthetic material,and the layered structure of carbon contributes to the migration of photoelectrons.The two-dimensional layered structure reduces the band gap of ceria semiconductor material due to the quantum confinement effect.Because of the unique4f electronic layer structure,ceria contains oxygen vacancies in the crystal lattice.Composite materials increase the oxygen vacancies due to the presence of biomimetic carbon,and the number of active sites is more abundant,which changes the position of the valence band and conduction band of the material and reduces the band gap of the composite material.All of these factors work together to improve the photocatalytic properties of the material.Chrysanthemums,begonia flowers,bamboo leaves and cherry blossoms are used as the template,after being impregnated with a solution of cerium nitrate and calcined,the carbon/ceria composites are obtained.The materials are characterized by the Thermogravimetric analyzer?TG-DSC?,X-ray Diffractometer?XRD?,Scanning Electron Microscope?FESEM?,High Resolution Transmission Electron Microscope?TEM?,Laser Raman Spectroscopy?Raman?,X-ray Photoelectron Spectrometer?XPS?and UV-Vis diffuse reflectance spectroscopy?UV-vis DRS?.The results show that the composite materials contain only carbon and ceria and no other impurities,retaining the original template morphology.The grain size of ceria in the composites using the four templates is 4 nm,5nm,7nm,and 12nm,respectively,and the utilization of visible light by the sample is higher than that of the reference cerium oxide.The content of oxygen defects in the samples is 65%,61%,57%,and 29%,and the proportion of Ce³⁺is 47%,35%,33%,and 26%,respectively.It can be seen that the smaller the size of ceria,the higher the proportion of oxygen defects inside the material.Comparison of hydrogen production by photocatalytic decomposition of water,the following conclusions are obtained:The yield of hydrogen produced by the chrysanthemum templated sample is the highest with the value is 380?mol/g,followed by the begonia flowers templated sample hydrogen production of 356?mol/g,and then the hydrogen yield of the bamboo leaf template is 337?mol/g.The worst effect is that the amount of hydrogen produced by the cherry blossoms template is 320?mol/g.In this order,the particle diameter distribution of ceria in the sample is from small to large,so it can be seen that the smaller particles are beneficial to improve the photocatalytic performance of the material.