Studies On Photocatalytic Performance And Modification Of MgWO₄ Material

As a clean and environmentally friendly technology,photocatalysis has attractive prospects in solving energy shortage and environmental pollution problems.In this paper,MgWO₄ nanosheets were synthesized by a simple hydrothermal method.The corresponding band structure was obtained by UV-Vis diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy,and the photocatalytic application potential of MgWO₄ nanosheets was theoretically demonstrated.Subsequently,the formation process of nanosheets was studied by time-gradient hydrothermal synthesis and its mechanism was proposed.At the same time,MgWO₄nanoparticles were synthesized by solvothermal method.X-ray diffraction（XRD）was used to analyze the crystal structure of these materials.Scanning electron microscope（SEM）and transmission electron microscope（TEM）were used to characterize the morphological differences between them.Their specific surface areas were calculated by the BET method.Photoluminescence spectra（PL）was carried out to evaluate the recombination of photogenerated carriers.Through a series of characterizations,the effect of morphology on the photocatalytic performance of MgWO₄ nanoplates and MgWO₄ nanoparticles was studied.In addition,the concentration of oxygen vacancies in MgWO₄ materials was successfully controlled by a simple high-temperature treatment in an argon atmosphere.According to electron paramagnetic resonance spectroscopy（EPR）,the oxygen vacancy concentration in the treated MgWO₄ material was greatly increased compared with the untreated MgWO₄ samples.On the one hand,the existence of oxygen vacancies will form a defect level below the conduction band of the semiconductor photocatalysts leading to reducing the band gap,thereby increasing the light absorption.And on the other hand,as the capture centers of photo-generated electrons,introduced oxygen vacancies will reduce the recombination rate of photo-generated carriers,thereby improving the photocatalytic activity.As the increased concentration of oxygen vacancy promotes the separation and migration of photogenerated electron-hole pairs,the photocatalytic hydrogen evolution rate of MgWO₄ material after atmosphere treatment is 81.5μmol/g/h,which is about 5.6times that of the untreated MgWO₄ samples（14.5μmol/g/h）.