CQDs-rGO/GF阴极电芬顿体系中过氧化氢的生成和对硝基苯酚的降解

Production of hydrogen peroxide and p-nitrophenol degradation by electro-Fenton system with CQDs modified rGO/GF cathode

对二维材料石墨烯进行表面修饰以提高其催化性能为目前较为重要的研究方向。利用水热法合成了直径5 nm的零维材料碳量子点(carbon quantum dots,CQDs),将其与还原石墨烯(reduced graphene oxide,rGO)进行结合,并载于石墨片(graphite flake,GF)表面制备了CQDs-rGO/GF复合电极。将该电极作为电芬顿体系的阴极,考察了CQDs对氧的二电子电化学还原生成过氧化氢的阴极反应的影响;以对硝基苯酚(p-nitrophenol,PNP)为目标污染物,考察了在Fe2+存在时该电芬顿体系对PNP的降解性能。结果表明:CQDs显著提高了阴极的活性,CQDs-rGO/GF阴极体系中过氧化氢的生成量是rGO/GF电极的1.9倍,是GF电极的2.4倍;在Fe2+存在时,该电芬顿体系对PNP的降解率达到90.6%,COD去除率为64.3%;羟基自由基是使PNP降解的主要活性物种。降解过程中PNP的UV-Vis谱图和COD去除率的变化均显示绝大部分PNP已被矿化,少量转化为小分子羧酸。以上研究结果表明,零维CQDs可用于提高二维材料rGO电极的催化性能。

Surface modification of a 2 D graphene for its catalytic performance improvement is an important research field.In this study,carbon quantum dots(CQDs)with 5 nm diameter and abundant edge defects were synthesized by hydrothermal method and combined with the reduced graphene oxide(rGO).The CQDs combined rGO were then deposited at a graphite flake(GF)to prepare a CQDs-rGO/GF electrode.This composite electrode was then applied as cathode to generate hydrogen peroxide through electro-reduction of oxygen.In the presence of Fe2+,the degradation of p-nitrophenol(PNP)in this electro-Fenton system was investigated.The experiment results showed that CQDs significantly improved the catalytic activity of rGO.The yield of hydrogen peroxide generated in the CQDs-rGO/GF cathode system was 1.9 times as much as that of rGO/GF electrode and 2.4 times as much as that of bare GF electrodes.In the presence of Fe2+,the degradation rate of PNP reached 90.6%and the removal rate of COD was 64.3%.Hydroxyl radical·OH was proved to be the main active species that degraded PNP.The changes of UV-Vis spectra of PNP and COD removal during the degradation process showed that most parts of PNP were mineralized,and a small amount of PNP was converted into smaller molecular carboxylic acids.This work concluded that zero dimensional CQDs could improve the performance of 2 D-rGO electrode.