Synthesis Of Ceria-Based Photocatalytic Materials And Modification Research

Photocatalysis is an emerging technology to degrade organic pollution and impro-ve ecological environment.The development of new and efficient photocatalyst is the key of photocatalytic technology.Nano-CeO2 has good application prospects in the field of photocatalysis because of its good UV absorption,oxygen storage and redox properties.However,CeO2 has a large band gap,which lead to less absorption of visible light and low utilization of solar energy,and the electron-hole recombination rate is high during photocatalytic process.This severely limits its catalytic efficiency.In this paper,the CeO2 lattice are doped with Fe and N elements to adjust the width of its band gap and increase the solar absorptivity.The surface area and quantum efficiency are improved by compounding with graphene.In addition,pure CeO2,flower CeO2 powder,different doping levels with Fe-CeO2 nanopowders and different nitrogen source doped N-10%Fe-CeO2 nanopowders are synthesised by hydrothermal or solvothermal method.The pure CeO2 powder and the flower CeO2 powder were successfully compounded with graphene by one-step method respectively.The microstructure and morphology were characterized by TEM,XRD,XPS,Raman and UV-Vis techniques.The photocatalytic performance was systematically studied by catalytic degradation of methylene blue solution experiment.The results show that,(1)The Fe and N elements doping do not change the crystal structure of CeO2,but they can adjust the CeO2 lattice parameters and band gap.For 0-15%Fe-doped CeO2 powders,the catalytic rate of 10%Fe-CeO2 is the fastest,and the degradation rate of methylene blue is increased from 67%to 95%.The catalytic rate of N-10%Fe-CeO2 prepared with concentrated ammonia(25%)as a nitrogen source was the fastest,whose degradation rate was further increased to 97%.The increase of catalytic activity of CeO2 is mainly due to the decrease of the band gap of CeO2 as the doping of Fe and N,which promotes the generation and reaction of electron-hole pairs.(2)The photocatalytic performance of CeO2 and graphene compound can be significantly improved.The CeO2-NPs can be evenly distributed on the graphene sheets.The degradation rate is increased from 67%to 88%with 31.3%enhancement.The CeO2-HFNs was covered and wrapped by graphene sheets,the degradation rate increased from 73%to 96%with 31.5%enthancemenr.The reason is mainly due to the graphene can reduce the agglomeration of CeO2 nanoparticles and flower CeO2,which can improve the specific surface area,and the photogenerated electrons can be more quickly transfer to the reaction activity point,which can improve the photoelectron-hole separation efficiency.Under the same conditions,the catalytic efficiency of the graphene composite flower CeO2 is higher than that of the graphene composite CeO2 nanoparticles.The main reason is that the CeO2 flower lamella has a large surface area and is not covered by graphene,while CeO2 nanoparticles are easy to agglomerate and have small specific surface area.Therefore,the former catalytic is more likely to have higher catalytic activity.