Preparation Of Vanadate/graphene Three-dimensional Composite Aerogel And Its Photocatalytic Properties

With the development of science and technology,environmental problems are becoming more and more serious.Among the numerous environment management techniques,the photocatalytic technique has a great potential in the widespread applications because of the high efficient and non-toxic advantages.In order to solve the problems such as low utilization efficiency and difficult recovery of powder catalyst in traditional TiO2 photocatalytic materials,composites were fabricated using vanadate with high visible light photocatalytic activity as the core material and the graphene as supporter in this paper.Three dimensional(3D)CeVO4/rGO and CeVO4/BiVO4/rGO composite aerogels were prepared by low temperature method and in situ hydrothermal method,respectively,which can not only improve the quantum efficiency of photocatalyst but also can be recycled easily.In this paper,the structure and morphology of the aerogels were characterized,and their photocatalytic properties were studied.The main conclusions are as follows:(1)The spindle shaped CeVO4 nano particles prepared by hydrothermal synthesis method were used as raw material.These CeVO4 particles were loaded onto the graphene supporter using low temperature method.CeVO4/rGO 3D composite material with high photocatalytic activity and stable performance was prepared.The photocatalytic properties of the CeVO4 particles and CeVO4/rGO composite were characterized by SEM,XRD and DRS etc.The results showed that the degradation efficiency of methylene blue(MB)was 62.1% for CeVO4 nanoparticles in 18 min.CeVO4/rGO airgel composite showed both higher catalytic activity(up to 93% for MB degradation)and convenient recovery.(2)In order to simplify the experimental steps and shorten the experimental period,CeVO4/rGO 3D aerogel was prepared by in-situ hydrothermal synthesis.The effects of different concentrations of GO,hydrothermal temperature and hydrothermal time on the photocatalytic activity of the resulting aerogels were investigated.The formation mechanism of CeVO4/rGO 3D aerogel was deduced,and the mechanism of photocatalyst was analyzed.The results showed that CeVO4 particles were in situ grown on the graphene nanosheets.The existence of graphene can effectively transfer the photogenerated electrons in CeVO4,which can improve the mobility of carriers and suppress the recombination of photogenerated electron-hole pairs.The specific surface area of the CeVO4/rGO aerogel is as high as 143.2m2/g.The above factors can effectively improve the photocatalytic activity of the CeVO4/rGO aerogel.The CeVO4/rGO prepared by 3mg/ml concentration of GO and heated 180? for 20 h showed the best photocatalytic property,and its degradation efficiency for MB was 95% within 18 min.(3)In order to further improve the photocatalytic performance,BiVO4 was introduced as the third phase,and the CeVO4/BiVO4/rGO 3D aerogels were also prepared by hydrothermal reaction method.The photocatalytic properties of the as-prepared 3D aerogels prepared using different ratios of BiVO4:CeVO4 ware studied.The photocatalytic mechanism of CeVO4/BiVO4/rGO was described in detail.The results showed that all of the obtained CeVO4/BiVO4/rGO composite samples maintained typical three-dimensional network structure.Due to the in-situ growth mechanism,BiVO4 and CeVO4 particles are dispersed in the skeleton graphene aerogel and combined with graphene sheets.The aerogel with the ratio of BiVO4: CeVO4 at 1:1 showed the best photocatalytic performance,high recovery efficiency and good cycling stability;and its degradation rate was 99.6% in 14 min.The photocatalytic activity of CeVO4/BiVO4/rGO was superior to CeVO4/rGO.The reason was supposed to be the change of the electron transition process of the semiconductor material,which can promote the separation of photoelectrons and holes more effectively and accelerate the catalysis rate.