Study On The Photocatalytic Performance Of Carbon Doped G-C3n4 Based On In Situ Photomicrocalorimeter-Fluorescence Spectrometry

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 photocatalyfie 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 pi forms amorphous carbon doping. The skeleton carbon doped g-C3N4 to form IT 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 center dot O-2. 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) mu J/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.