石墨相氮化碳的红外辅助微波法制备及光催化固氮性能

doi:10.7503/cjcu20160148

摘要/Abstract

摘要：

采用红外辅助微波法制备了可见光下具有优越固氮性能的石墨相氮化碳催化剂(g-C₃N₄). 采用X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、氮气吸附、紫外-可见光谱(UV-Vis)、荧光光谱(PL)、 N₂-程序升温脱附(TPD)和电子顺磁共振谱(EPR)等对催化剂进行了表征. 结果表明, 微波处理在催化剂表面形成许多孔状结构, 增大了催化剂的比表面积, 抑制了催化剂光生电子-空穴的复合; 微波处理还会产生大量氮空穴, 这些氮空穴一方面可以吸附并活化氮气分子, 另一方面可提升电荷从催化剂到氮气分子的界面转移能力, 显著提高催化剂的光催化固氮性能. 采用红外辅助微波法制备的g-C₃N₄催化剂比采用单纯微波法制备的催化剂具有更多的氮空穴, 表现出更高的光催化固氮性能.

关键词: 红外辅助微波法, 石墨相氮化碳, 固氮, 氮空穴, 光催化

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

中图分类号:

O644

TrendMD:

曹宇辉, 佟宇飞, 张健, 李法云, 范志平, 白金, 毛微, 胡绍争. 石墨相氮化碳的红外辅助微波法制备及光催化固氮性能. 高等学校化学学报, 2016, 37(7): 1357.

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^†. Chem. J. Chinese Universities, 2016, 37(7): 1357.

图/表 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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