Design and Synthesis of FeAl2O4-based Visible-light-driven Photocatalysts and Their Photocatalytic Properties

Author:Mu Hui Ying

Supervisor:hu yong zuo


Degree Year:2017





With the rapid development of modern industry,environmental pollution has become one of the most severe problems in the world.Spinel-structured hercynite has obtained attention as a prospective material with considerable potential application in degradation of environmental organic pollutants,because of its advantages such as excellent chemical stability,inexpensive,nontoxicity,photochemical and thermal stability.Nevertheless,few reports on the hercynite expound the effect of the practical application and experiment investigation in the photocatalysis field,due to complicated equipment or long consuming time which was essential in the preparation process of hercynite.In this paper,earth-abundant FeAl2O4-based nanomaterials were prepared via facile solution combustion synthesis and used as photocatalysts.Density functional theory and scanning Kelvin probe technique were employed to ascertain the positions of energy bands and Fermi level.Meanwhile,the relationship between phtotocatalytic activity and transfer properties of photoinduced charge carriers was discussed.The purpose was to build FeAl2O4-based photocatalytic materials with low-cost,high efficiency,and phase matching.Firstly,the mesoporous earth-abundant FeAl2O4 photocatalyst was synthesized via one-step solution combustion route and its electronic structure was revealed by density functional theory (DFT) calculation and scanning Kelvin probe (SKP) technique measurement.The experiment results indicated that FeAl2O4 was a kind of indirect transition semiconductor and had a narrow band-gap of 1.78 eV.The type and amount of fuel had important influence on the compositions and properties of the combustion products.The photocatalytic activity was evaluated by the degradation of high concentration phenol.The crystallinity degree was the decisive factor in determining the seperation efficiency of photo-generated charge carriers in spite that the oxygen adsorption ability and superoxide anion radicals played important influence on the degradation of phenol.The information providing here should be in favour of designing and synthesis of high performance photocatalysts.Then,a series of FeAl2O4/Al2O3 heterojunctions were prepared by a hydrothermal synthesis approach and the properties of photogenetated charges were studied by PL and SPV techniques.The findings were as follows:The as-synthesised FeAl2O4/Al2O3 hybrids displayed much higher photocatalytic activity than the pure Al2O3 and FeAl2O4 nanoparticles.The seperation efficiency of photo-generated charge carriers and the photocatalytic mechanism in the degradation of phenol had been discussed.Al2O3 which acted as electron acceptors can effectively inhibit the charge recombination of FeAl2O4/Al2O3 composites.To make use of molecular oxygen (O2) existed in the atmosphere,a series of FeAl2O4/g-C3N4 composites had been synthesized.On the basis of our experimental results,the molecular oxygen activation performance and photocatalytic mechanism were discussed for enhanced visible-light-driven photocatalysis.The results showed that electron transfer from the g-C3N4 conduction band (CB) to the FeAl2O4 CB could effectively separate the photo-generated electrons and holes,which thereby reduced their recombination.And the g-C3N4–originating holes would then move from the valence band (VB) of g-C3N4 to the FeAl2O4 VB.The as-prepared FeAl2O4/g-C3N4heterojunctions exhibited superior molecular oxygen activation performance via electron transfer route.This work would provide valuable references in the application of FeAl2O4-based materials to prepare heterojunctions and be beneficial to the development of low-cost photocatalysts and the design thoughts of molecular oxygen activation.