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新型BiOI/g-C3N4纳米片复合光催化剂的制备及其可见光催化活性增强
引用本文:安华,林波,薛超,严孝清,代艳竹,魏进家,杨贵东.新型BiOI/g-C3N4纳米片复合光催化剂的制备及其可见光催化活性增强[J].催化学报,2018,39(4):654-663.
作者姓名:安华  林波  薛超  严孝清  代艳竹  魏进家  杨贵东
作者单位:西安交通大学化学工程与技术学院,西安交通大学-牛津大学催化国际联合实验室,陕西西安710049 西安交通大学电子与信息工程学院,电子陶瓷与器件教育部重点实验室,陕西西安710049
基金项目:陕西省自然科学基础研究计划,国家自然科学基金,重质油国家重点实验室开放基金,中央高校基本科研业务费,This work was supported by the Natural Science Basic Research Plan in Shaanxi Province of China,the National Natural Science Foundation of China,State Key Laboratory of Heavy Oil Processing,the Fundamental Research Funds for the Central Universities,Thanks for the technical support from International Center for Dielectric Research,Xi'an Jiaotong University
摘    要:近年来, 石墨型氮化碳(g-C3N4)作为一种n型半导体光催化剂材料, 由于具有较好的热稳定性和化学稳定性, 同时具有可调的带隙结构和优异的表面性质而备受人们关注. 然而, 传统的g-C3N4块体材料存在比表面积小、光响应范围窄和光生载流子易复合等缺陷, 制约着其光催化活性的进一步提高. 因此, 人们开发了多种技术对块体状g-C3N4材料进行改性,其中构建基于g-C3N4纳米薄片的异质结复合光催化材料被认为是强化g-C3N4载流子分离效率, 进而提高其可见光催化活性的重要手段. BiOI作为一种窄带隙的p型半导体光催化剂, 具有强的可见光吸收能力和较高的光催化活性, 同时它与g-C3N4纳米薄片具有能级匹配的带隙结构. 因此, 基于以上两种半导体材料的特性, 构建新型的BiOI/g-C3N4纳米片复合光催化剂材料不仅能够有效提高g-C3N4的可见光利用率, 而且还可以在n型g-C3N4和p型BiOI界面间形成内建电场, 极大促进光生电子-空穴对的分离与迁移效率.为此, 本文通过简单的一步溶剂热法在g-C3N4纳米薄片表面原位生长BiOI纳米片材料, 成功制备了新型的BiOI/g-C3N4纳米片复合光催化剂. 利用X射线衍射仪(XRD), 场发射扫描电子显微镜(SEM)、透射电子显微镜(TEM)、紫外-可见漫反射光谱和瞬态光电流响应谱对所合成复合光催化剂的晶体结构、微观形貌、光吸收性能和电荷分离性能进行了表征测试. XRD, SEM和TEM结果显示, 结晶完好的BiOI呈小片状均匀分散在g-C3N4纳米薄片表面; 紫外漫反射光谱表明, 纳米片复合材料的吸光性能较g-C3N4薄片有显著提升; 瞬态光电流测试证明, 复合材料较单一材料有更好的电荷分离与迁移性能.在可见光催化降解RhB的测试中, BiOI/g-C3N4纳米片复合光催化剂显示出了优异的催化活性和稳定性, 其光降解活性分别为纯BiOI和g-C3N4的34.89和1.72倍; 自由基捕获实验发现, 反应过程中的主要活性物种为超氧自由基(·O2-), 即光生电子主导整个降解反应的发生. 由此可见, 强的可见光吸收能力和g-C3N4与BiOI界面处形成的内建电场协同促进了g-C3N4纳米薄片的电荷分离, 进而显著提高了该复合材料的可见光催化降解活性. 此外, 本文初步验证了在BiOI/g-C3N4纳米片复合光催化体系内光生电荷是依据"双向转移"机制进行分离和迁移的, 而非"Z型转移"机制.

关 键 词:g-C3N4  BiOI  纳米片  光降解  双向转移  可见光  g-C3N4  BiOI  Nanosheet  Photodegradation  Double-transfer  mechanism  Visible  light
收稿时间:30 October 2017

Formation of BiOI/g-C3N4nanosheet composites with high visible-light-driven photocatalytic activity
Hua An,Bo Lin,Chao Xue,Xiaoqing Yan,Yanzhu Dai,JinJia Wei,Guidong Yang.Formation of BiOI/g-C3N4nanosheet composites with high visible-light-driven photocatalytic activity[J].Chinese Journal of Catalysis,2018,39(4):654-663.
Authors:Hua An  Bo Lin  Chao Xue  Xiaoqing Yan  Yanzhu Dai  JinJia Wei  Guidong Yang
Institution:1. XJTU-Oxford International Joint Laboratory for Catalysis, School of Chemical Engineering and Technology, Xi''an Jiaotong University, Xi''an 710049, Shaanxi, China;2. Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education, Center for Dielectric Research, Xi''an Jiaotong University, Xi''an 710049, Shaanxi, China
Abstract:Constructing binary heterojunctions is an important strategy to improve the photocatalytic perfor-mance of graphitic carbon nitride (g-C3N4). In this paper, a novel g-C3N4nanosheet-based composite was constructed via in situ growth of bismuth oxyiodide (BiOI) nanoplates on the surface of g-C3N4 nanosheets. The crystal phase, microstructure, optical absorption and textural properties of the synthesized photocatalysts were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy (DRS), and nitrogen adsorption-desorption isotherm measurements. The BiOI/g-C3N4 nanosheet composite showed high activity and recyclability for the photodegradation of the target pollutant rhodamine B (RhB). The conversion of RhB (20 mg L-1) by the photocatalyst was nearly 100% after 50 min under visible-light irradiation. The high photoactivity of the BiOI/g-C3N4 nanosheet composite can be attributed to the enhanced visible-light absorption of the g-C3N4 nanosheets sensitized by BiOI nanoplates as well as the high charge separation efficiency obtained by the establishment of an internal electric field between the n-type g-C3N4and p-type BiOI. Based on the characterization and experimental results, a double-transfer mechanism of the photoinduced electrons in the BiOI/g-C3N4nanosheet composite was proposed to explain its activity. This work represents a new strategy to understand and realize the design and synthesis of g-C3N4 nanosheet-based heterojunctions that display highly efficient charge separation and transfer.
Keywords:BiOI  Nanosheet  Photodegradation  Double-transfer mechanism  Visible light
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