Abstract:

In this study, a perylene tetracarboxylic dianhydride (PTCDA)-modified graphitic carbon nitride (g-C₃N₄) composite photocatalyst (PI-g-C₃N₄) was synthesized via thermal polymerization. The photocatalytic degradation efficiency of phenol (Ph) via PI-g-C₃N₄/Vis system and its possible reaction mechanism were systematically investigated. The prepared PI-g-C₃N₄ composite photocatalyst was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), UV-Vis diffuse reflectance spectroscopy (UV-Vis-DRS), transient photocurrent response analysis and Mott-Schottky (M-S) plots. The effects of different catalysts, catalyst dosages, initial solution pH and different actual water backgrounds on the photocatalytic degradation of Ph were evaluated. The results demonstrated that under xenon lamp irradiation (with a filter for λ>400nm) with a PI-g-C₃N₄ dosage of 1.0g/L, an initial Ph concentration of 10mg/L and a reaction time of 120min, the removal efficiency of Ph reached 91% with a degradation rate constant of 0.02min^-1, which was 10 times and 250 times of Ph degradation by g-C₃N₄ or PTCDA alone. The dosage of catalyst and alkaline condition were all favorable for Ph degradation. Radical quenching experiments and electron spin resonance (ESR) analysis revealed that photogenerated holes (h⁺), superoxide radicals (O₂^•-) and hydrogen peroxide (H₂O₂) were the primary active species responsible for Ph degradation. PI-g-C₃N₄ was an S-scheme heterostructure, where PTCDA was coupled with g-C₃N₄ through π-π conjugation interactions. This configuration effectively facilitated the separation of photogenerated electron-hole pairs, ultimately leading to significant enhancement in photocatalytic degradation performance for Ph. Furthermore, recycling experiments confirmed the excellent reusability of the PI-g-C₃N₄ composite catalyst. This study provided new insights and methodologies for the application of photocatalytic materials in environmental pollution control.

Key words: photocatalysis, graphitic carbon nitride, perylene tetracarboxylic dianhydride, phenol degradation

摘要：

采用热聚合法制备了苝四羧酸二酐（PTCDA）修饰的石墨相氮化碳（g-C₃N₄）光催化剂（PI-g-C₃N₄），并研究其光催化降解苯酚（phenol，缩写为Ph）的效果及其可能的光催化反应机制。采用扫描电子显微镜（SEM）、透射电子显微镜（TEM）、X射线衍射（XRD）、傅里叶变换红外吸收光谱（FTIR）、X射线光电子能谱仪（XPS）、UV-Vis漫反射光谱（UV-Vis-DRS）、光电流分析、莫特-肖特基（Mott-Schottky，M-S）曲线等方法对制备的PI-g-C₃N₄光催化剂进行表征。考察了不同催化剂、催化剂投加量、不同溶液初始pH、不同实际水体对光催化降解Ph的影响。结果表明，当利用氙灯（配置波长大于400nm的滤光片）作为光源，催化剂PI-g-C₃N₄投加量为1.0g/L、污染物Ph初始浓度为10mg/L、反应120min时，Ph的去除率可达91%，且降解Ph的速率常数为0.02min^-1，是单独g-C₃N₄或PTCDA降解Ph的10倍和250倍。催化剂投加量和碱性条件均有利于Ph的降解。自由基淬灭实验和电子自旋共振实验结果证明，该体系中光生空穴（h⁺）、超氧自由基（O₂^•-）和过氧化氢（H₂O₂）是降解Ph的主要活性物种。PI-g-C₃N₄为S型异质结构，通过π-π共轭相互作用将PTCDA与g-C₃N₄结合，有效促进了光生电子-空穴对的分离，实现了光催化降解Ph的性能提升。最后，催化剂循环利用实验证明了制备的PI-g-C₃N₄光催化剂具有较好的重复利用性。本研究旨在为光催化材料在环境污染治理领域提供新思路和新方法。

关键词: 光催化, 石墨相氮化碳, 苝四羧酸二酐, 苯酚降解