Preparation And Application Of Novel Phosphate Photocatalysts

In recent years,photocatalytic technology has attracted much attention due to its potential application in solving pollution problems.So,many people make efforts to find novel efficient photocatalysts.Among diverse photocatalytic materials,BiPO₄has been widely investigated because of the excellent property,such as good stability,nontoxicity,low-cost and fast separation.In this paper,BiPO₄,g-C₃N₄/BiPO₄ and BiVO₄/BiPO₄ composites were synthesized by different methods,and characterized by X-ray diffraction?XRD?,scanning electron microscopy?SEM?,UV–vis diffuse reflection spectroscopy?DRS?and Fourier transformed infrared spectra?FTIR?.The effects of different synthesis methods and reaction conditions on photocatalytic activity of the samples were systematically studied.Subsequently,the mechanism of photodegradation of organic dyes was analyzed.The main results are as follows:?1?Hydrothermal method,microwave assisted method and microwave method were explored for the synthesis of different bismuth-based photocatalysts with the same raw materials.The results showed that the sample synthesized by hydrothermal method presented monoclinic monazite BiPO₄,and sample prepared by microwave assisted method was mixed crystal phases BiPO₄ with monazite and hexagon structure.However,the sample fabricated via microwave method was Bi₆O₅?OH?₃?NO₃?₅·2H₂O.Under ultraviolet light irradiation,the sample prepared by microwave assisted method exhibited the highest photocatalytic activity,it removed 99.7%of methylene blue?MB?within 10 min.The rate constant of the sample prepared by microwave assisted method is almost 11.66 times as high as that of the sample synthesized by microwave method.?2?The g-C₃N₄/BiPO₄ composites were synthesized by hydrothermal method.The results showed that CN-Bi-2 exhibited the highest photocatalytic activity,it degraded 98.95%of rhodamine B?RhB?after simulated sunlight irradiation for 5 h.The photocatalytic activity of CN-Bi-2 was 17%higher than that of pure BiPO₄,and the rate constant was 2.65 times as high as the pure BiPO₄.A possible reason for the improved photocatalytic activity of g-C₃N₄/BiPO₄ was attributed to the transfer of photogenerated electrons and holes.When BiPO₄ was combined with g-C₃N₄,different energy band structures of semiconductors led to the transfer of photogenerated carriers.So,g-C₃N₄/BiPO₄ composite can improve the charge separation and suppress the recombination of photogenerated electrons and holes,which result in the higher photocatalytic activity.?3?BiVO₄/BiPO₄ composites were synthesized by microwave assisted method.The influence of the V/P molar ratio and the microwave power on photocatalytic activity was explored.Experiment results showed that BiVO₄/BiPO₄ composites exhibited a much higher photocatalytic activity than that of pure BiPO₄.15%V/P degraded 99.60%of MB after visible light irradiation for 60 min,while the degradation rate for pure BiPO₄ was only about 33.54%.Microwave power had an effect on the photocatalytic activity,samples with the power lower than 150 W exhibited poor photocatalytic activity.The results showed that the photocatalytic activity of the sample prepared by two-step was not much different from that of the sample prepared by one-step.So,the sample prepared by one-step has a better application prospect than the sample prepared by two-step because of the simple process.