Chinese Journal of Catalysis ›› 2019, Vol. 40 ›› Issue (3): 424-433.DOI: 10.1016/S1872-2067(18)63183-3

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

Xibao Lia, Jie Xionga, Ying Xub, Zhijun Fenga, Juntong Huanga   

  1. 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:2018-08-28 Revised:2018-10-09 Online:2019-03-18 Published:2019-02-22
  • Supported by:

    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: Photocatalyst, Heterojunction, Direct Z-scheme, Doping, Modification