Preparation Of Cerium Oxide-based Composite Material And Its Photocatalytic Performance

With the rapid development of industry,environmental problems that are caused by the discharge of industrial wastewater are increasing.Photocatalytic technology driven by solar energy is a green and sustainable technology and one of the most effective ways to solve problems related to energy and the environment.As a typical rare earth oxide,CeO₂has important physical and chemical properties.In general nano-CeO₂,Ce³⁺and Ce⁴⁺coexist and contain a certain amount of oxygen vacancies.Oxygen vacancies play a role in the catalytic process,so they are often used in photocatalytic degradation of organic dyes.However,the band gap of cerium oxide is large(3.1 e V),which cannot make good use of visible light.The electron-hole recombination rate of single-component cerium oxide is relatively high,so the photocatalytic effect of single cerium oxide is limited.Aiming at the above-mentioned shortcomings,this paper proposes various strategies for the modification of CeO₂photocatalytic materials to improve its photocatalytic performance.The main contents and conclusions of this research are as follows:(1)The flower-like CeO₂/MoS₂heterojunction was composed by self-assembly of MoS₂nanoflowers and ultrafine CeO₂nanoparticles through high-temperature nitrogen annealing.The crystal structure,morphology,specific surface area,chemical state,and optical properties of flower-like CeO₂/MoS₂heterostructure material were analyzed by XRD,SEM,(HR)TEM,BET,XPS,UV-Vis,and PL characterization methods.Flower-like CeO₂/MoS₂heterostructure material has a large specific surface area and strong adsorption capacity.In the photodegradation of methyl orange,the20%CeO₂/MoS₂material has the best photocatalytic performance,the degradation efficiency of 20%CeO₂/MoS₂reaches 96.1%in 90 min and the reaction rate constant(k)is 0.0325 min^-1,far exceeding the single-component MoS₂and single-component CeO₂.After detailed analysis,we know that the large specific surface area,excellent visible light absorption,and rapid separation of electron-hole pairs help to effectively improve photocatalytic efficiency.(2)The monodisperse core-shell structure CeO₂nanospheres were prepared by hydrothermal and thermal decomposition methods without adding a template,and Ag nanoparticles were grown in situ on the CeO₂shell surface through mercury lamp irradiation to synthesize Ag-modified cerium oxide nanospheres(Ag-CeO₂)with a core-shell structure.The local plasmon resonance(LSPR)effect of Ag nanoparticles on the surface of CeO₂effectively enhances the visible light absorption and photo-generated electron-hole separation efficiency of the Ag-CeO₂sample.Compared with single-component CeO₂nanospheres,Ag-CeO₂samples have better photocatalytic performance.Under simulated sunlight,the degradation rate of the Ag-CeO₂sample to methyl orange reached 93.2%in 2 h.(3)Hollow Cu/CeO₂@mSiO₂(CDC@mSiO₂)samples were prepared by calcining Cu²⁺doped Ce-Ui O-66 precursor coated with mesoporous silica(mSiO₂).BET analysis shows that CDC@mSiO₂has a mesoporous structure and a large specific surface area(397.7 m²/g),which can provide a lot of active sites for photocatalytic reactions.Ultraviolet absorption spectrum and PL spectrum show that the introduction of Cu²⁺makes the absorption edge of the sample red-shift and accelerate the separation efficiency of electrons and holes.The CDC@mSiO₂sample has the best photodegradation efficiency.Under simulated sunlight,the degradation rate of methyl orange within 2 hours is 92.6%,and the photocatalytic rate constant is0.0221 min^-1.After 4 cycles of experiments,it still has excellent photocatalytic activity.Based on the characterization analysis and experimental results,the degradation mechanism of methyl orange is proposed.