Preparation Of Polypyrrole-based Photocatalysts And Redox Properties

With the development of industry,various pollutants such as Cr（Ⅵ）and organic dyes in wastewater were increasing day by day,which brings serious harm to the ecological environment.Photocatalytic technology has shown more and more significant application potential in the treatment of water pollutants,and photocatalyst was the core of this technology.As an excellent electricity and holes transporter,conjugated polymer polypyrrole（PPy）was considered as the most promising photocatalytic composite modified material due to its unique photoelectric characteristics,good environmental stability,low cost and simple preparation.PPy and inorganic nano semiconductor materials coupling,not only to compensate for their own defects but also due to the synergies between the two could got more excellent performance.At present,PPy based composite materials had been applied in the fields of photoelectrocatalysis,sensors,electrode materials,solar cells and so on.In this paper,PPy as the base material,PPy and inorganic semiconductor materials were composite,methylene blue（MB）and Cr（Ⅵ）as the target pollutants,performance-oriented design and construction of a series of PPy based composite photocatalytic materials,in order to improve the charge transfer properties and achieve the improvement of photocatalytic performance.Combing with a variety of characterization methods,the photocatalytic redox mechanism of PPy composite photocatalytic materials was systematically explored.This work provides an effective method for the preparation of an efficient and stable photocatalyst.The specific research contents were as follows:As one of the common conductive polymers,polypyrrole has the characteristics of high conductivity,low oxidation potential,good stability in air and easy preparation.It could be used in photocatalytic materials,electrode materials,biosensors,anticorrosive materials,antistatic materials and electroluminescent materials and other industrial fields.Therefore,the preparation and application properties of polypyrrole and its composites were of great significance.The main research contents and achievements are as follows:1.The PPy photocatalyst materials doped with Cl^-,SO₄^2-and Ts O^-were prepared by in situ oxidation polymerization,and the species of dopants were adjusted.It was found that p-toluenesulfonic acid（Ts OH）as Ts O^-source can increase the polymerization degree and conjugation degree of the intrinsic state PPy,and gradually change the pyrrole ring from aromatic to a quinone.The interchain order degree of PPy was increased,and the separation and transfer efficiency of the hole-electron pairs were improved.The results showed that PPy prepared with Ts OH as dopant showed good photocatalytic activity for reducing Cr（Ⅵ）and oxidizing MB.2.A new type of PPy/Zn Ti-LDH composite was successfully synthesized by in-situ oxidation polymerization.It was found that the introduction of PPy improved the visible light absorption range and light absorption intensity of Zn Ti-LDH.The reduction rate of Cr（Ⅵ）was nearly 99.79%within 40 minutes,and the rate constants k were 53 and 12 times of the Zn Ti-LDH and PPy,respectively.The degradation rate of MB was 77.12%in 80 minutes.After 5 cycles,the Cr（Ⅵ）reduction performance can reach 95.10%,indicating that PPy/Zn Ti-LDH composite has excellent photocatalytic stability.3.P-n type heterojunction Bi OBr/PPy composite photocatalytic material was successfully constructed by in-situ oxidation polymerization.The effects of PPy content on the photocatalytic performance of composite materials were investigated under visible light.1.5%PPy/Bi OBr showed the best photocatalytic activity,the reduction rate of Cr（Ⅵ）was 100%,and the degradation rate of MB was 99.72%.After 5 cycles of use,the photocatalytic activity did not decrease significantly.It shows excellent stability.It was found that the photocatalytic improvement of composite materials was mainly due to the formation of p-n type heterojunction,which promoted the separation and transfer of electron holes,and finally greatly improved the photocatalytic activity.