Preparation And Environmental Application Of MOFs/Vanadate Composite Photocatalytic Materials

Photocatalysis technology can degrade pollutants with sunlight as the driving force without secondary pollution,so it has great application prospect in the field of environmental remediation.Furthermore,the powder catalyst can be prepared on the membrane electrode with applied voltage,which could realize the simple recovery of the catalyst and maintain high activity.At present,a great deal of researches are focused on the development of new and efficient photocatalytic materials,with a view to further improving the solar energy utilization rate and photocatalytic efficiency.Metal-organic framework（MOFs）materials have high specific surface area and structural controllability.Their HUMO and LOMO energy levels can play the role similar to the conduction band（CB）and valence band（VB）in semiconductors,becoming a popular photocatalytic materials.Therefore,this paper takes MOFs as the research object to prepare efficient photocatalytic composite materials by constructing heterogeneous junctions.First,prepared the classic MOFs material（HKUST-1）by electrochemical method,and FeVO₄ was further loaded on it as a substrate,and FeVO₄/HKUST-1 composite material was obtained by precipitation at room temperature.Morphological structure,photoelectric response ability and photocatalytic activity were investigated to identified FeVO₄ was wrapped in HKUST-1 crystal surface with amorphous.The formation of the composite material has a smaller radius of the impedance of the loop.It also can produce higher photoelectric response and stronger ability of photocatalytic degradation of dye contaminant.Take Rh B(1×10^-5 mol/L)as the simulated pollutant,FeVO₄/HKUST-1 can completely degraded Rh B under the light condition of pH 3 in120 minutes,and also has good cycling stability.In addition,electrode materials based on FeVO₄ and BiVO₄ were prepared,then loaded with HKUST-1 and NH₂-MIL-125（Ti）respectively by solvothermal method.Among these photoelectrocatalysis electrodes,BiVO₄/NH₂-MIL-125 electrode was selected to make further research for it has the best photoelectric catalytic performance.Combined with the characterization of XRD,SEM,XPS and photoelectric catalytic performance tests of LSV,M-S curve and EIS,it can be found that BiVO₄ and NH₂-MIL-125（Ti）form heterogeneous junction structure,which improved the photoelectric catalytic performance of the electrode.By changing the load ratio and substrate concentration,the best preparation conditions were optimized,and the optimum application conditions were obtained by comparing the degradation effects of different reaction conditions.That is,under pH 3,applied 2 V bias and visible light irradiation,the removal rate of the optimal electrode was nearly 100%on 5 mg/L phenol within150 minutes,and the catalytic performance remained good after multiple cycles.Furthermore,the BiVO₄/NH₂-MIL-53/NH₂-MIL-125 electrode was prepared by solvothermal method.Through the characterization of the morphology and structure of the electrode,it was found that NH₂-MIL-53（Fe）and NH₂-MIL-125（Ti）were equably loaded on the BiVO₄ substrate,with integrated structure and enough contact.The optimal catalytic performance was obtained when the molar ratio of NH₂-MIL-53（Fe）and NH₂-MIL-125（Ti）was 0.2:0.8 by optimizing the load ratio and load concentration.Combined with the electrochemical performance test and the photoelectric catalytic degradation test of phenol,it is found that the ternary composite electrode has the highest photoelectric performance,the minimum transfer resistance and the highest photoelectric conversion efficiency.Experiments under different conditions showed that phenol could be completely degraded by photoelectricity in 120 minutes under the conditions of pH 3,bias pressure of 2 V and visible light irradiation,with good cycling stability.