The synthesis of photocatalysts based on graphitic carbon nitride (g-C₃N₄) and their application on NO degradation under visible light

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The synthesis of photocatalysts based on graphitic carbon nitride (g-C₃N₄) and their application on NO degradation under visible light

 

Author: Zheng, Qinmin
Title: The synthesis of photocatalysts based on graphitic carbon nitride (g-C₃N₄) and their application on NO degradation under visible light
Degree: M.Sc.
Year: 2013
Subject: Photocatalysis.
Hong Kong Polytechnic University -- Dissertations
Department: Faculty of Construction and Environment
Pages: ix, 68 leaves : col. ill. ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2646940
URI: http://theses.lib.polyu.edu.hk/handle/200/7183
Abstract: Indoor air quality attracts more and more attention for its health effects. Photocatalysis offers a promising alternative for indoor air pollutants removal and graphitic carbon nitride (g-C₃N₄), a novel metal free photocatalyst which can absorb visible light, is worth to be explored the application in air purification under visible light. In this research, we applied this material in photodegradation of NO, a common indoor pollutant with the concentration at ppb level. To investigate the effects of precursor, template, and metal doping on the structure, morphology and photocatalytic performance of g-C₃N₄, a series of photocatalysts, bulk g-C₃N₄, Mesoporous g-C₃N₄, Zn doped mesoporous g-C₃N₄, were synthesized and characterized by XRD, Nitrogen sorption measurements, SEM and UV-vis spectroscope, then their photocatalytic performances were evaluated by photodegradating NO at ppb level. The main research results are as follows: (i) The effects of precursor on the property could be investigated from the comparison of the two bulk g-C₃N₄ synthesized from Urea and Thiourea. The result shows the surface area of g-C₃N₄-Urea (100 m²/g) is much larger than g- C₃N₄-Thiourea (18 m²/g), which may indicate that oxygen and sulfur, play a very important role in the processing of carbon nitride condensation, and oxygen is found to be more efficient for enlarging the surface area of g-C₃N₄. The larger surface area makes g-C₃N₄-Urea has a higher NO removal efficiency even the g-C₃N₄-Thiourea has a better visible light absorption. (ii) The mesoporous g-C₃N₄ could be generated with the addition of SiO₂ as the hard template, and their surface areas and pore volumes are both improved when compared with bulk g-C₃N₄, which result in the remarkable enhance of the photocatalytic performance on NO removal. (iii) Zn doping may affect the structure and morphology of g-C₃N₄, like the surface area and pore size. In the meantime, it can also change the photochemical properties. The photocatalytic performance result shows Zn doping mpg-C₃N₄-Urea has the highest NO removal efficiency, reaching to 40%, 10% percent higher than mpg-C₃N₄-Urea without doping. The improvement may due to the increase of the optical absorption, resulting in more electronhole pairs generated in g-C₃N₄ with the doping of Zn. It might also due to that the doping facilitate the separation of those electron-hole pairs.

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