Controlled Fabricationand Photocatalytic Performance Of3DOM InVO₄and CrO_x/3DOM InVO₄for The Oxidative Removal Of Organic Pollutants

There are numerous organics in the wastewater, which seriously pollute the waterenvironment and influence the life of animal and botany. Therefore, it is ofsignificance to eliminate the organic compounds in the wasterwater. In recent years,the removal of organics from the wasterwater by the photocatalysis technology hasbeen one of the hot topics. Among the large number of photocatalysts, the mostlyinvestigated TiO2semiconductor with a wide bandgap is only responsive to ultravioletlight and can not response to solar light, and hence its applications are limited. InVO₄is a novel visible-light-driven photocatalyst with a narrow bandgap and shows goodphotocatalytic activities for many reactions. In this thesis, three-dimensionally orderedmacroporous （3DOM） monoclinic InVO₄with mesoporous skeletons and itssupported chromia （yCrO_x/3DOM InVO₄） photocatalysts were prepared using theorganic acid-assisted polymethyl methacrylate （PMMA）-templating and incipientwetness impregnation methods, respectively. Physical properties of the materials werecharacterized by means of a number of analytical techniques, such as X-raydiffraction （XRD）, thermogavimetric analysis （TGA）, differential scanningcalorimetry （DSC）, scanning electron microscopy （SEM）, transmission electronmicroscopy （TEM）, selected-area electron diffraction （SAED）, N2adsorption-desorption （BET）, X-ray photoelectron spectroscopy （XPS）, andultraviolet-visible diffuse reflectance spectroscopy （UV-Vis DRS）. Photocatalyticactivities of the as-obtained photocatalysts were evaluated for the degradation ofmethylene blue （MB） and rhodamine B （RhB） under the visible-light illumination.The main results obtained in the present thesis are as follows:1. The3DOM-structured monoclinic InVO₄photocatalysts with mesoporouswalls were prepared adopting the citric acid （CA）-, tartaric acid （TA）-or ascorbic acid（AA）-assisted PMMA-templating strategy with In（NO3）34.5H2O and NH4VO3asmetal source, and ethylene glycol （EG） and absolute methanol （MeOH） as solvent. Theas-obtained photocatalysts possessed a macropore diameter of130170nm, amesoporous size of540nm, a surface area of35.152.3m2/g, and a bandgap energyof2.502.75eV。During the photocatalyst preparation process, the used complexingagents and solvent volumetric ratios were the important factors influencing the porousstructure of the final InVO₄product. The InVO₄photocatalyst derived with PMMA inthe presence of AA, MeOH, and EG （MeOH/EG volumetric ratio=7.5/1.5） possessedthe best quality in3DOM architecture, the largest surface area, and the lowest bandgap energy, and hence showing the best photocatalytic performance for the degradation ofMB. It is concluded that the excellent photocatalytic activity of this photocatalyst wasrelated to its larger surface area, higher surface oxygen vacancy density, and lowerbandgap energy as well as the better3DOM structure quality.2. The3DOM-structured monoclinic InVO₄photocatalyst with mesoporous wallswas prepared using the AA-assisted PMMA-templating strategy with In（NO3）34.5H2Oand NH4VO3as metal source, and ethylene glycol （EG） and absolute methanol （MeOH）as solvent. Three-dimensionally ordered macroporous （3DOM） monoclinicInVO₄-supported chromia （yCrO_x/3DOM InVO₄; y is the mass percentage of Cr2O3, y=5,10,15, and20wt%） photocatalysts were prepared using the incipient wetnessimpregnation method with Cr（NO3）3.9H2O as metal source. The as-obtainedyCrO_x/3DOM InVO₄photocatalysts exhibited a surface area of41.345.0m2/g and abandgap energy of2.102.38eV. The loading of CrO_xdid not lead to a change incrystal structure of InVO₄. Compared to the3DOM InVO₄photocatalyst, theyCrO_x/3DOM InVO₄photocatalysts showed higher surface oxygen vacancy density,lower bandgap energy, and better optical absorption ability. With the loading of CrO_x,the photocatalytic activity of the photocatalyst first increased and then decreased, andreached the highest at a CrO_xloading of15wt%. The15CrO_x/3DOM InVO₄with asurface area of45.0m2/g and a bandgap energy of2.10eV exhibited the bestphotocatalytic activity for the degradation of RhB in the presence of a small amount ofH2O2under visible-light illumination. It is concluded that the CrO_xloading, largersurface area, and higher surface oxygen vacancy density, and lower bandgap energy aswell as the better3DOM structure quality were responsible for the excellentphotocatalytic performance for RhB degradation.