Polyoxometalates/TiO₂ Composite Photocatalyst Interfacial Charge Regulation And Coupling Advanced Oxidation Application

With the continuous development of modern industry,the discharge of wastewater containing a large number of pollutants into the nature leads to the increasingly serious environmental pollution problems.It is a great challenge for the research field of water treatment to seek new pollutant removal technologies that meet the requirements of sustainable development in the future.Due to its low energy consumption,wide application range,no secondary pollution,green and high efficiency,the application of photocatalytic oxidation in environmental restoration has attracted extensive attention in recent years.Titanium dioxide（TiO₂）with abundant reserves,environmental friendliness and high catalytic activity is regarded as the most promising photocatalytic material.However,the industrial application of TiO₂ is seriously limited by its narrow spectral utilization range and high carrier recombination probability（3.2 eV forbidden band width）.In order to obtain the further improvement of photocatalytic performance,it is particularly important to find an effective way of photogenic charge separation.That of this paper is to build more acid molecular modification of TiO₂ composite photocatalyst,on the basis of charge separation process by introducing structural defects on heterogeneous interface controls,deeply reveals more acid compound,heterostructure is built,and defect formation strategy for composite photocatalyst in photocatalytic auxiliary class fenton and light catalytic activation persulfate type coupling,such as the application of the advanced oxidation reaction.The main research contents are as follows:（1）Based on the reconstruction of the Iron phosphotungstate（Fe-POM）load defect P25:photocatalyst on P25 oxygen vacancy defects in structure of TiO₂,on the basis of further regulation by impregnation method to load more iron acid molecules to the surface of a different state of surface of TiO₂,check defect formation and secondary reconstruction light catalytic-class fenton synergy effects on the activity of catalytic degradation of organic dyes.The results showed that the ability of P25 photocatalytic degradation of pollutants introduced by oxygen vacancy in H₂atmosphere treatment was enhanced,and the spatial distribution of oxygen vacancy was reconstructed after the compound calcining of cyanamide.The reconstructed defects were more conducive to the transfer of photogenerated charge on the surface of P25 to Fe-POM molecules.With the improvement of the photogenic charge separation ability of P25 photocatalyst and the enhancement of the active site of fenton reagent,the defective fenton photocatalyst showed a 13-fold increased catalytic activity in the degradation of methylene blue（MB）dye.（2）Composite construction of defective TiO₂ nanowires and（Fe-POM）to construct fenton-like photocatalyst:in order to further enhance the active sites of the composite photocatalyst,Fe-POM were combined with the prepared TiO₂ to construct fenton-like photocatalyst with defect regulation.Experiments show that the composite catalyst based on one-dimensional TiO₂nanowires preparation than P25 system has higher specific surface area,the oxygen vacancy introduction and defect reconstruction can also promote the photoproduction electronic shift to more acid molecules,so that the defect reconstruction of fenton light catalyst in co-treating organic dyes and the reaction of 5-sulfosalicylic acid（SSA）in efficiency compared with original TiO₂ 5times and 3.5 times.Superoxide radicals（·O₂^-）and hydroxyl radicals（·OH）generated by fenton-like reactions on the surface of photocatalyst activated by oxygen vacancy are the main reasons for the enhanced degradation efficiency.（3）The crystal surface Fe-POM/TiO₂ was used as a photocatalyst to activate the persulfate degradation system of organic pollutants:the high-energy{001}exposed surface TiO₂ was used,and the Fe-POM/TiO₂/PS coupling system was designed.Through the synergistic effect of photocatalysis and persulfate activation,the bisphenol A（BPA）degradation ability of the catalyst was significantly improved.The removal rate of bisphenol A in Fe-POM/TiO₂/PS system was 7times and 18 times higher than that in Fe-POM/TiO₂ photocatalytic system and photoactivated persulfate system,respectively.Studies show that the enhanced catalytic activity is mainly attributed to the generation of a large number of SO₄^-·and·OH radicals.Based on the above research,the interface of charge efficient separation was constructed based on the strategies of crystal surface engineering and defect control,and a new way was provided for further coupling reaction processes such as fenton and persulfate activation to treat pollutants in water,which provided beneficial reference for the development of coupling advanced oxidation technology.