Chemical Journal of Chinese Universities ›› 2020, Vol. 41 ›› Issue (11): 2526-2537.doi: 10.7503/cjcu20200292

• Physical Chemistry • Previous Articles     Next Articles

Study on the Photocatalytic Performance of Carbon Doped g-C3N4 Based on in situ Photomicrocalorimeter-fluorescence Spectrometry

MA Xiangying1, LIAO Yanjun2, QIN Fanghong1, YIN Yuanhao1, HUANG Zaiyin1(), CHEN Qifeng1()   

  1. 1.College of Chemistry and Chemical Engineering
    2.College of Marine and Biotechnology,Guangxi University for Nationalities,Nanning 530008,China
  • Received:2020-05-26 Online:2020-11-10 Published:2020-11-06
  • Contact: HUANG Zaiyin E-mail:huangzaiyin@163.com;cqf408@163. com
  • Supported by:
    Supported by the National Natural Science Foundation of China(Nos.21573048, 21873022), the Basic Ability Improvement Project for Young and Middle?aged Teachers in Guangxi, China(Nos.2017KY0167, 2018KY0165), the Scientific Research Project of Guangxi University for Nationalities, China(No.2017MDYB007), the Natural Science Foundation of Guangxi Province, China(No.2017JJA120714y) and the Experimental Technology Innovation and Laboratory Management Research Project of Guangxi University for Nationalities, China(No.2016MDSY008).

Abstract:

Carbon-doped graphite nitride(g-C3N4) was synthesized by adding tannic acid to urea precursor. X-ray photoelectron spectroscopy(XPS), field emission scanning electron microscopy(FESEM), X-ray diffractometer(XRD), synchronous thermal analysis(TG-DSC) and other methods were used to characterize the morphology phase and valence components of carbon doped g-C3N4. The photocatalytic degradation mechanism of Rhodamine B was investigated by using UV-Vis and in situ photomicrocalorimeter-fluorescence spectrometry to obtain in situ thermodynamics/kinetic information and 3D fluorescence spectral information of the degradation of Rhodamine B by carbon doped g-C3N4.The results showed that, when the tannic acid concentration was ≤10 mg/mL, the carbon would replace nitrogen atoms in the unit structure of heptazine to form g-C3N4 skeleton carbon doping. When the tannic acid concentration is ≥20 mg/mL, the carbon deposition load on the surface of g-C3N4 in amorphous form forms amorphous carbon doping . The skeleton carbon doped g-C3N4 to form π electrons effectively shorted the band gap width and reduced the photoelectron-hole recombination probability, showing excellent photocatalytic performance. The main active species of catalysis were h+ and ·O2-. The photocatalytic degradation process of carbon doped g-C3N4 can be divided into three processes: endothermic of light responds, the balance process of endothermic of light responds and exothermic of pollutant degradation, and stable exothermic. The intensity of fluorescence emission peak of Rhodamine B over skeleton carbon doped g-C3N4(C/N=0.844) decreased sharply within the illumination of 1000 s, its degradation rate reached 87.6%,which was 3.13 times and 1.95 times over original g-C3N4 and amorphous carbon doped g-C3N4, respectively. After illumination of 1000 s, the photodegradation of the ring and intermediates without fluorescent chromophores were dominated, which maintained a stable exothermic rate of (0.9799±0.5356) μJ/s with a pseudo-zero order process. This process was the rate-determining step. Therefore, Rhodamine B photocatalysis was a pseudo-zero-order process rather than a first order process.

Key words: g-C3N4, Doping, Photocatalyst, Photomicrocalorimeter, In situ fluorescence spectrum

CLC Number: