一步法合成磷掺杂石墨相氮化碳及其光催化性能

doi:10.15541/jim20160256

摘要/Abstract

摘要：

以尿素(CO(NH₂)₂)和磷酸氢二铵((NH₄)₂HPO₄)作为原料, 通过热聚合法制备了磷(P)掺杂石墨相氮化碳(g-C₃N₄)材料(P-CN)。通过X射线衍射、红外光谱、X射线光电子谱、扫描电子显微镜、透射电子显微镜、紫外可见漫反射光谱和N₂吸附-脱附对样品进行了表面形貌及结构表征, 通过对罗丹明B(RhB)的降解实验, 研究了样品的可见光催化性能, 对其催化机理进行了分析。结果表明, 合成过程中磷原子的掺杂会取代g-C₃N₄中的C原子, 从而改变g-C₃N₄的表面形貌和电子结构。在可见光条件下, P-CN材料表现出优异的光催化性能, 其对RhB的降解速率明显优于纯氮化碳。其中3%P-CN样品催化活性最高, 反应30 min时, RhB降解率达到96.8%。分析认为, P原子对g-C₃N₄中的C原子的取代使P-CN样品表面处于富电子状态, 并导致P-CN样品导带位置升高, 光电子还原性增强。这些电子与水中的溶解氧形成超氧自由基(·O₂^-), 从而使得光催化性能显著提高。

关键词: 磷, 氮化碳, 可见光, 光催化

Abstract:

A series of P-doped g-C₃N₄(P-CN) samples were prepared using urea (CO(NH₂)₂) and diammonium hydrogen phosphate ((NH₄)₂HPO₄) as raw materials by a simple thermal condensation method. The surface morphologies and structures of the as-prepared samples were characterized by X-ray diffraction (XRD), fourier transform infrared spectroscope (FT-IR), X-ray photoelectron spectroscope(XPS), scanning electron microscope (SEM), transmission electron microscope (TEM), UV-Vis diffuse reflection spectra (UV-Vis DRS) and N₂ adsorption-desorption isotherms, respectively. The visible-light photocatalytic property was demonstrated for photodegradation of Rhodamine (RhB) solution, and the photocatalytic mechanism for the P-CN samples under visible-light was tentatively proposed. The corresponding results indicate that C atoms in g-C₃N₄ are replaced by P atoms, which modifies the surface morphologies and electronic structures. The as-prepared P-CN samples show remarkably higher photocatalytic efficiency than pure g-C₃N₄ for RhB degradation under visible-light irradiation. 3%P-CN sample demonstrates the highest photocatalytic activity, which degrades 96.8% RhB after reaction for 30 min. The replacement of P to C atoms in g-C₃N₄ makes the surface of P-CN in an electron-rich state. Furthermore, the research indicates the conduction band of P-CN shifts to more negative values, which improves the reduction performance of photoelectron. The electrons in conduction band of P-CN reduce O₂ to ·O₂^- in the reaction system, so that the photocatalytic property are improved significantly.

Key words: phosphorus, g-C3N4, visible-light, photocatalysis

中图分类号:

TQ174

徐赞, 于薛刚, 单妍, 刘峰峰, 张宪明, 陈克正. 一步法合成磷掺杂石墨相氮化碳及其光催化性能[J]. 无机材料学报, 2017, 32(2): 155-162.

XU Zan, YU Xue-Gang, SHAN Yan, LIU Feng-Feng, ZHANG Xian-Ming, CHEN Ke-Zheng. One-pot Synthesis of Phosphorus Doped G-C₃N₄ with Enhanced Visible-light Photocatalytic Activity[J]. Journal of Inorganic Materials, 2017, 32(2): 155-162.

图/表 12

图1 样品的XRD图谱

Fig. 1 XRD patterns of the as-prepared photocatalysts

图2 样品的FT-IR谱图

Fig. 2 FT-IR spectra of the as-prepared photocatalysts

图3 样品的(a) C1s、(b) N1s和(c) P2p的X射线光电子谱图; g-C3N4和3%P-CN的价带谱图, 图中内嵌的是方框区域的放大图(d)

Fig. 3 XPS spectra of (a) C1s, (b) N1s and (c) P2p for 3%P-CN and XPS valence band (VB) spectra of g-C3N4 and 3%P-CN (d) with inset showing the magnification of the area marked with a box

图4 不同样品的扫描电镜照片及其EDS谱图

Fig. 4 SEM images and EDS pattern of the as-prepared photocatalysts (a) g-C3N4; (b) 1% P-CN; (c) 3% P-CN; (d) 5% P-CN; (e) 7% P-CN; (f) 9% P-CN; (g) EDS pattern of 3%P-CN

图5 不同样品的透射电镜照片

Fig. 5 TEM images of the as-prepared photocatalysts(a) g-C3N4; (b) 1% P-CN; (c) 3% P-CN; (d) 5% P-CN; (e) 7% P-CN; (f) 9% P-CN

表1 EDS测量的3%P-CN样品中各元素含量

Table1 Element contents of 3%P-CN measured by EDS

Element	wt%	at%
C K	33.42	37.81
N K	54.31	52.70
P K	2.29	1.01
O K	9.98	8.48
Total	100	100

图6 样品在可见光条件下对RhB的降解曲线

Fig. 6 Degradation curves of RhB under visible-light irradiation over g-C3N4 and P-CN

图7 3%P-CN的循环使用性能降解曲线

Fig. 7 Cycling runs for the photocatalytic degradation of RhB over 3%P-CN under visible-light irradiation

图8 样品的氮气吸附-脱附曲线

Fig. 8 N2 adsorption-desorption isotherms of the as-prepared photocatalysts

图9 样品的紫外-可见漫反射吸收光谱

Fig. 9 UV-Vis diffuse reflectance spectra of the photocatalysts

图10 捕获剂对降解效率的影响

Fig. 10 Effects of a series of scavengers on the degradation efficiency

图11 P-CN样品催化机理示意图

Fig. 11 Schematic illustration for photocatalytic mechanism of P-CN samples under visible-light irradiation

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