Study On The Effects Of Inorganic Ions On The Photocatalytic Performance Of TiO₂ Nanotube Arrays

TiO₂ nanotube arrays have good photoelectric performance,chemical stability,reusability,etc.so they have a wide range of applications in the fields of degradation of organic matter,dye-sensitized solar cells,and photocatalytic hydrogen production.However,the presence of inorganic ions in industrial wastewater will have a certain effect on the photocatalytic performance of TiO₂.Although there are also some studies to explore the mechanism,we still have not been able to reach a consensus.In addition,most of the current researches are based on the preparation of samples with titanium sheets,and the opaqueness of titanium sheets will result in lower light utilization and increase the operating and maintenance costs of industrial production.These problems will hinder the promotion of TiO₂ photocatalysis in industrial applications.In order to solve the above problems,based on the preparation of TiO₂ nanotube on the titanium substrate,the titanium mesh-based TiO₂ nanotube arrays were successfully prepared by anodization and slow-temperature heat treatment.And we also researched the effect of ions on photocatalytic performance.The specific results are as follows:（1）The effects of inorganic anions in wastewater on photocatalytic performance were investigated.The presence of SO₄^2-can significantly improve the photocatalytic reaction activity,the reaction constant is 1.28 times that of the non-additive group,while CO₃^2-,PO₄^3-,NO₂^-,S^2-,and CrO₄^2-will inhibit the photocatalytic reaction activity.The mechanism of improving the photocatalytic performance of SO₄^2-was studied,it was considered that holes are trapped during the reaction,and the recombination of electrons and holes is suppressed.At the same time,strongly oxidizing·SO4^-is formed,which is water-soluble and can react homogeneously with pollutant molecules in the liquid phase.The homogeneous reaction of the molecules is the essence of improving the photocatalytic performance.（2）The effect of the presence of cations was tested.Among them,Fe³⁺can significantly increase the photocatalytic reaction rate.The main mechanism is that a cyclic conversion reaction of Fe³⁺and Fe²⁺occurs in the reaction system,It suppresses the recombination of electrons and holes,and promotes the production of·OH,thereby promoting the reaction.（3）TiO₂ nanotubes with anatase/rutile mixed crystal phase were successfully prepared.By adjusting the heat treatment process and holding time,a sample ATONA（T）-1 with optimal photocatalytic performance was prepared,and its photocatalytic performance was improved by 22.0%.And in conjunction with the promotion of inorganic ions,the photocatalytic performance was further improved to 35.4%.From the perspective of charge recombination,a semi-quantitative analysis of the enhancement of photocatalytic efficiency was conducted,and it was found that the maximum inhibition efficiency of carrier recombination by SO₄^2-and mixed crystal phase structures was 47.7%and 66.2%,respectively.