Infrared Ray Assisted Microwave Synthesis of Graphitic Carbon Nitride and Its Nitrogen Photofixation Ability†

doi:10.7503/cjcu20160148

Abstract

Abstract:

A convenient infrared ray assisted microwave method was used to synthesize graphitic carbon nitride(g-C₃N₄) with outstanding nitrogen photofixation ability under visible light. X-ray diffraction(XRD), N₂ adsorption, UV-Vis spectroscopy, scanning electron microscopy(SEM), transmission electron microscopy(TEM), N₂-temperature programmed desorption(TPD), electron paramagnetic resonance(EPR), photoluminescence spectroscopy(PL) and photocurrent measurements were used to characterize the prepared catalysts. The results indicate that microwave treatment can form many irregular pores in the as-prepared g-C₃N₄, which causes the increased surface area. More importantly, microwave treatment causes the formation of many nitrogen vacancies in the as-prepared g-C₃N₄. These nitrogen vacancies not only serve as active sites to adsorb and activate N₂ molecules but also promote the interfacial charge transfer from catalysts to N₂ molecules and the separation rate of electrons-hole pairs, thus significantly improving the nitrogen photofixation ability. The higher nitrogen vacancy concentration of g-C₃N₄ prepared by infrared ray assisted microwave treatment causes the more chemisorption sites, leading to the higher nitrogen photofixation performance. This method is simple and convenient, and is suitable for large-scale production of g-C₃N₄ catalyst.

Key words: Infrared ray assisted microwave method, Graphitic carbon nitride(g-C3N4), N2 photofixation, Nitrogen vacancy, Photocatalysis

CLC Number:

O644

TrendMD:

CAO Yuhui, TONG Yufei, ZHANG Jian, LI Fayun, FAN Zhiping, BAI Jin, MAO Wei, HU Shaozheng. Infrared Ray Assisted Microwave Synthesis of Graphitic Carbon Nitride and Its Nitrogen Photofixation Ability^†[J]. Chem. J. Chinese Universities, 2016, 37(7): 1357.

Figures/Tables 10

Fig.1 Nitrogen photofixation ability of catalysts prepared by different microwave treating time(A) and photocatalytic stability of IM-CN(30)(B)

Fig.2 Effect of NaNO2 concentration(a) and flow rate(b) on N2 photofixation ability over as-prepared IM-CN(30)

Fig.3 XRD patterns of as-prepared catalysts under microwave(A) and infrared ray assisted microwave(B) treatment(A) a. CN520; b. M-CN(15); c. M-CN(20); d. M-CN(25). (B) a. CN520; b. IM-CN(20); c. IM-CN(25); d. IM-CN(30).

Fig.4 SEM images of as-prepared CN520(A), M-CN(20)(B), IM-CN(30)(C) and HRTEM image of IM-CN(30)(D)

Fig.5 Nitrogen adsorption-desorption isotherms of CN520(a), M-CN(20)(b) and IM-CN(30)(c)

Fig.6 UV-Vis spectra of CN520(a), M-CN(20)(b) and IM-CN(30)(c)

Fig.7 EPR spectra of CN520(a), M-CN(20)(b) and IM-CN(30)(c)

Fig.8 N2-TPD curves of as-prepared CN520(a), M-CN(20)(b) and IM-CN(30)(c)

Fig.9 PL spectra of as-prepared CN520(a), M-CN(20)(b) and IM-CN(30)(c) under N2 atmosphere(A) and comparison of PL intensity of the samples under Ar or N2 atmospheres(B)

Fig.10 Photocurrent response of as-prepared catalysts under N2 or Ar atmospheres(A) a. CN520/N2; b. M-CN(20)/N2; c.IM-CN(30)/N2. (B) a. CN520/Ar; b. IM-CN(30)/Ar; c. CN520/N2; d.IM-CN(30)/N2.

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