Preparation And Performance Study Of CQDs-based Nanocomposite Photocatalyst

In order to solve the problem of high carrier complexation rate and poor photocatalytic performance of carbon quantum dots(CQDs),BiOCl and Poly-p-phenylenediamine(PpPD)were selected in this thesis to compound with CQDs,respectively,by improving the photogenerated charge separation efficiency of CQDs and thus their photocatalytic activity.The synergistic catalytic degradation is innovatively achieved by introducing microwave source combined with photocatalysis technology,and further by introducing microwave induction lamp to convert microwave energy into light energy to improve the photocatalytic activity of the material.The following two main results were obtained in the paper.Firstly,CQDs/BiOCl composites were prepared by microwave hydrothermal method by selecting semiconductor BiOCl as the carrier,and the composite structure of spherical CQDs tightly attached to the surface of BiOCl two-dimensional sheet layer was obtained.The process conditions were optimized by adjusting the composite ratio of the two materials and the duration of microwave irradiation during the preparation process.The experimental results showed that CQDs/BiOCl-1 had the highest photocatalytic activity at 30 min of microwave irradiation,with 91%degradation of 30 ppm RhB solution at 5.0 min and 73%degradation of 50 ppm RhB solution at 10 min.Finally,the photocatalytic mechanism of CQDs/BiOCl complexes was discussed.And then,in order to more fully utilize the microwave energy in the MEDL system,poly-p-phenylenediamine(PpPD),which has microwave absorption capability,was selected as a carrier to be compounded with CQDs.The CQDs/PpPD composite was prepared by microwave melting method,which is a complex of irregular PpPD flakes with uniformly distributed CQDs of 2.0-5.0 nm in diameter on the surface.The prepared CQDs/PpPD composite photocatalyst has a type Ⅱ heterogeneous structure,which not only has a strong visible and UV light absorption,but also has a greatly reduced complexation rate of electron-hole pairs.Under MEDL conditions,the degradation efficiency of 50 ppm RhB reached 91.8%in 10 min.After four cycles,the degradation rate was stable at over 88%.In addition,its photocatalytic mechanism was explored,and three main reasons for the efficient photocatalytic performance of CQDs/PpPD composite catalysts were derived.(1)the CQDs/PpPD composites have a wide range of light absorption and high light absorption intensity;(2)CQDs/PpPD with type II heterostructures can achieve efficient carrier separation;(3)microwaves and light play a synergistic role,which effectively improves the photocatalytic performance of CQDs/PpPD composites.