缺陷辅助表面修饰提高g-C3N4@C-TiO2直接Z型异质结的可见光光催化性能

引用本文: 李喜宝, 熊杰, 许英, 冯志军, 黄军同. 缺陷辅助表面修饰提高g-C₃N₄@C-TiO₂直接Z型异质结的可见光光催化性能[J]. 催化学报, 2019, 40(3): 424-433. doi: 10.1016/S1872-2067(18)63183-3 shu

Citation: Xibao Li, Jie Xiong, Ying Xu, Zhijun Feng, Juntong Huang. Defect-assisted surface modification enhances the visible light photocatalytic performance of g-C₃N₄@C-TiO₂ direct Z-scheme heterojunctions[J]. Chinese Journal of Catalysis, 2019, 40(3): 424-433. doi: 10.1016/S1872-2067(18)63183-3 shu

缺陷辅助表面修饰提高g-C₃N₄@C-TiO₂直接Z型异质结的可见光光催化性能

李喜宝 ^a, ,
熊杰 ^a, ,
许英 ^b, ,
冯志军 ^a, ,
黄军同 ^a,

a 南昌航空大学材料科学与工程学院, 江西南昌 330063;
b 湖南科技大学物理与电子科学学院, 湖南湘潭 411201
基金项目:
国家自然科学基金（51772140）；江西省自然科学基金（20161BAB206111，20171ACB21033）；江西省教育厅科技项目（GJJ170578）.

摘要: 光催化技术被认为是解决能源和环境问题的最有前途方法之一.较高光催化活性的石墨相氮化碳（g-C₃N₄）及碳掺杂TiO₂（C-TiO₂）的制备及性能一直是环境光催化研究的热点，然而，单一光催化剂存在光生电子空穴易复合及量子效率低等问题.
本课题组曾通过简单的水辅助煅烧法成功制备了纳米多孔g-C₃N₄，结果发现，多孔g-C₃N₄光催化活性较体相的明显提高，但光催化效率仍不够理想，原因是光生电子空穴复合较严重.传统的制备C-TiO₂的方法亦存在一些不足，如需要添加碳源或碳组分聚集体.我们采用原位掺杂的方法合成了含有一定氧空位和活性位的纳米碳改性的C-TiO₂，后辅以简单的化学气相沉积法构建了g-C₃N₄表面修饰的g-C₃N₄@C-TiO₂.结果表明，相比纯g-C₃N₄，TiO₂及C-TiO₂，g-C₃N₄@C-TiO₂具有更高的光催化活性；但其原因及碳掺杂态的影响尚不清楚.基于此，本文采用X射线光电子能谱技术（XPS）、透射电子显微镜（TEM）、电化学阻抗谱（EIS）、光致发光谱（PL）、电子顺磁共振技术（EPR）及理论计算等手段研究了g-C₃N₄@C-TiO₂光催化活性提高的原因和机理.
XPS结果表明，随着碳含量的增加，间隙掺杂产生的O-C键的峰值强度先增大后趋于稳定，而晶格取代掺杂产生的Ti-C键的峰值强度逐渐增大.Ti-O峰的减少进一步证明了更多的碳取代了氧晶格的位置.随着碳掺杂量的增加，C-TiO₂的带隙逐渐减小，因而吸收边红移；同时，g-C₃N₄@C-TiO₂的光催化降解效率先升高后降低.g-C₃N₄@C-TiO₂对RhB（苯酚）光降解的最大表观速率常数为0.036（0.039）min^-1，分别是纯TiO₂，10C-TiO₂，g-C₃N₄和g-C₃N₄@TiO₂的150（139），6.4（6.8），2.3（3）和1.7（2.1）倍.g-C₃N₄通过π-共轭和氢键与C-TiO₂表面紧密结合，在催化剂中引入了新的非局域杂质能级和表面态，可以更有效地分离和转移光生电子，因而光催化活性增加.由此可见，碳掺杂状态和g-C₃N₄原位沉积表面改性对g-C₃N₄@C-TiO₂复合光催化剂性能的影响很大.

关键词:

光催化剂
/ 异质结
/ 直接Z型
/ 掺杂
/ 修饰

English

Defect-assisted surface modification enhances the visible light photocatalytic performance of g-C₃N₄@C-TiO₂ direct Z-scheme heterojunctions

a School of Materials Science and Engineering, Nanchang Hangkong University, Nanchang 330063, Jiangxi, China;
b School of Physics and Electronic Science, Hunan University of Science and Technology, Xiangtan 411201, Hunan, China
Received Date: 28 August 2018
Revised Date: 09 October 2018
Fund Project:
This work was supported by the National Natural Science Foundation of China (51772140), the Natural Science Foundation of Jiangxi Province, China (20161BAB206111, 20171ACB21033) and the Scientific Research Foundation of Jiangxi Provincial Education Department, China (GJJ170578).

Abstract: To increase the number of active sites and defects in TiO₂ and promote rapid and efficient transfer of photogenerated charges, a g-C₃N₄@C-TiO₂ composite photocatalyst was prepared via in situ deposition of g-C₃N₄ on a carbon-doped anatase TiO₂ surface. The effects of carbon doping state and surface modification of g-C₃N₄ on the performance of g-C₃N₄@C-TiO₂ composite photocatalysts were studied by X-ray diffraction, X-ray photoelectron spectroscopy, UV-visible diffuse-reflectance spectroscopy, transmission electron microscopy, electrochemical impedance spectroscopy, photoluminescence, and electron paramagnetic resonance. With increasing carbon doping content, the carbon doping state in TiO₂ gradually changed from gap to substitution doping. Although the number of oxygen vacancies gradually increased, the degradation efficiency of g-C₃N₄@C-TiO₂ for RhB (phenol) initially increased and subsequently decreased with increasing carbon content. The g-C₃N₄@10C-TiO₂ sample exhibited the highest apparent reaction rate constant of 0.036 min^-1 (0.039 min^-1) for RhB (phenol) degradation, which was 150 (139), 6.4 (6.8), 2.3 (3), and 1.7 (2.1) times higher than that of pure TiO₂, 10C-TiO₂, g-C₃N₄, and g-C₃N₄@TiO₂, respectively. g-C₃N₄ was grown in situ on the surface of C-TiO₂ by surface carbon hybridization and bonding. The resultant novel g-C₃N₄@C-TiO₂ photocatalyst exhibited direct Z-scheme heterojunctions with non-local impurity levels. The high photocatalytic activity can be attributed to the synergistic effects of the improved visible light response ability, higher photogenerated electron transfer efficiency, and redox ability arising from Z-type heterojunctions.

Key words:

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缺陷辅助表面修饰提高g-C₃N₄@C-TiO₂直接Z型异质结的可见光光催化性能

English

Defect-assisted surface modification enhances the visible light photocatalytic performance of g-C₃N₄@C-TiO₂ direct Z-scheme heterojunctions

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