机械混合法制备TiO_(2)/g-C_(3)N_(4)复合材料及其光催化降解双酚A的性能

Preparation of TiO_(2)/g-C_(3)N_(4) composite material by mechanical mixing method and study on its photocatalytic degradation performance of bisphenol A

本工作采用机械混合方法,将TiO_(2)纳米颗粒与不同质量的g-C_(3)N_(4)复合,制备了一系列具有不同g-C_(3)N_(4)含量的TiO_(2)/g-C_(3)N_(4)复合材料.运用X射线粉末衍射(XRD)、X射线光电子能谱(XPS)、拉曼光谱(Raman)、比表面积分析仪(BET)、扫描电镜(SEM)和透射电镜(TEM)对材料的化学组成和形貌特征进行了表征.比较了g-C_(3)N_(4)、TiO_(2)和一系列TiO_(2)/g-C_(3)N_(4)在可见光驱动下对水中双酚A(BPA)的降解效率和矿化能力差异,发现TiO_(2)/g-C_(3)N_(4)的光催化活性显著高于g-C_(3)N_(4)和TiO_(2),其中以TiO_(2)/g-C_(3)N_(4)-B的光催化活性最高(g-C_(3)N_(4)的投料量为0.08 g).为了揭示TiO_(2)/g-C_(3)N_(4)良好光催化活性的产生机理,采用紫外可见光谱、稳态和瞬态荧光光谱对催化剂(以TiO_(2)/g-C_(3)N_(4)-B为研究模型)可见光响应能力、带隙结构以及光生载流子分离能力进行了分析.结果证实,通过机械混合方法向TiO_(2)体系引入适量的g-C_(3)N_(4)不仅能够将TiO_(2)的光响应范围拓宽,而且可以提升光生载流子的分离能力并延长载流子存活寿命.此方法构建的复合材料能够在水环境中保持结构和性能的稳定.对降解过程中自由基分布特征的监测表明,降解过程中的主要活性物种为空穴自由基和羟基自由基.

In this work,a series of TiO_(2)/g-C_(3)N_(4) composites with different g-C_(3)N_(4) content were prepared by combining TiO_(2) nanoparticles with g-C_(3)N_(4) of different masses through using a mechanical mixing method.The chemical composition and morphological structure of the composites were analyzed by X-ray powder diffraction(XRD),X-ray photoelectron spectroscopy(XPS),Raman spectroscopy(Raman),Brunauer-Emmett-Teller(BET),scanning electron microscope(SEM)and transmission electron microscope(TEM).Driven by visible light,the differences in degradation efficiency and mineralization ability of bisphenol A(BPA)in water with g-C_(3)N_(4),TiO_(2) and a series of TiO_(2)/g-C_(3)N_(4) were compared.Among them,TiO_(2)/g-C_(3)N_(4)-B has the highest photocatalytic activity(the content of g-C_(3)N_(4) is 0.08 g).To reveal the generation mechanism of the good photocatalytic activity of TiO_(2)/g-C_(3)N_(4),UV-visible spectroscopy,steady-state and transient fluorescence spectroscopy were used to analyze the visible light response capability,band gap structure,and photogenerated carrier separation ability of the catalyst(using TiO_(2)/g-C_(3)N_(4)-B as the research model).The results confirmed that the introduction of an appropriate amount of g-C_(3)N_(4) into the TiO_(2) system through the mechanical mixing method can not only broaden the photoresponse range of TiO_(2),but also enhance the separation ability of photogenerated carriers and extend the carrier lifetime.The composite material constructed by this method can maintain the stability of structure and performance in the water environment.The monitoring of the distribution characteristics of radicals shows that the main active species in the degradation process are hole and hydroxyl radicals.