The Synthesis And Photoactivity Evaluation Of BiVO₄-based Composite Photocatalyst

With the economic development of society,the problems of environmental pollution and energy shortage had been become highlighted sharply.The traditional biological oxidation and chemical treatment technology can not meet the needs of people's lives,in the degradation process of organic pollutants,semiconductor photocatalytic technology had been paid more and more attention due to the characteristics of economy,good degradation,and no pollutions.However,TiO₂ is the representative of the traditional photocatalysts due to the wide band gap of 3.2 e V,so that it can only use 3%⁵%of the ultraviolet light in the sunlight,resulting in quantum efficiency is low.Based on the theory analysis of microstructure,the development of high efficiency and wide spectral response new photocatalytic materials for improving the utilization ratio of visible light is a current research hotspot and difficulty.BiOI/BiVO₄,BiVO₄/MWCNT and BiVO₄/RGO composites were synthesized by sol-gel method,through a series of characterization methods to reveal the structure and morphology of synthetic materials.The research achieve the following results:BiOI/BiVO₄,MWCNT/BiVO₄ and RGO/BiVO₄ heterojunction photocatalysts were synthesized by complexing Sol-Gel method,using RhB as the model pollutant,in which the influence of photocatalytic activity and stability on the catalytic reaction were considered,the samples were characterized by using X-ray diffraction?XRD?,scanning electron microscopy?SEM?,Transmission electron microscope?TEM?,Fourier transform infrared spectroscopy?FT-IR?,UV-Vis absorption spectroscopy X-ray photoelectron spectroscopy?XPS?.The results indicated that we have reported heterojunction structure of monoclinic BiOI-BiVO₄ fabricated,depositing BiVO₄ nanoflakes onto the surface of BiOI,it played a crucial role that heterojunction structure of BiOI-BiVO₄ in electronic-hole recombination,and improving the quantum efficiency,the BiOI/BiVO₄ photocatalyst exhibited more strong absorbance than BiVO₄.The photocatalytic activity and stability of the Bi OI/BiVO₄ composites for photodegradation of RhB were efficient and much higher than that of the pure BiVO₄,it was found that 20mol%BiOI/BiVO₄ exhibited the highest photocatalytic degradation efficiency which was 95.7%.The analyses indicate that MWCNT/BiVO₄ photocatalysts are monoclinic phase,the phase of BiVO₄ is not changed after introduction of CNT,CNT nanoparticles are uniformly distributed on the surface of BiVO₄,it is the good conductivity and surface area of MWCNT that enhance the active sites on the surface of the catalyst,also they maintain their own valence condition that MWCNT and BiVO₄ existing in the MWCNT-BiVO₄ compound system,and the composite structure is the heterostructure,the enhancing photocatalytic activity of MWCNT/BiVO₄ is attributed to the efficient separation of electron-hole pairs derived from the heterostructure is formed by the matching ba nd potentials between MWCNT and BiVO₄.The photocatalytic activity and stability of the MWCNT/BiVO₄ composites for photodegradation of RhB are efficient and much higher than that of the pure BiVO₄ crystals,It is found that 2w%MWCNT/BiVO₄ exhibites the highest photocatalytic degradation efficiency and had a better stability.The analysis results indicated that a series of heterojunction structure RGO/BiVO₄composite photocatalysts were synthesized successfully,and all were monoclinic crystal structure,the phase of BiVO₄ was not changed after introduction of RGO,BiVO₄ nanoflakes were distributed on the surface of RGO,BiVO₄ and RGO existed in the composite system,the heterostructure had formed,because of the good conductivity and large surface area of RGO,the active sites of the composites were increased,it played a crucial role that the heterostructure in electronic-hole recombination,the results showed that the photocatalytic performance of BiVO₄/RGO was greatly enhanced,BiVO₄/RGO had more strong light response.It was interesting that 6w%BiVO₄/RGO exhibited the highest photocatalytic degradation efficiency and stability.