高可见光催化降解污染物和产氢活性的Z型N-掺杂K4Nb6O17/g-C3N4异质结

doi:10.1016/S1872-2067(20)63608-7

催化学报 ›› 2021, Vol. 42 ›› Issue (1): 164-174.DOI: 10.1016/S1872-2067(20)63608-7

高可见光催化降解污染物和产氢活性的Z型N-掺杂K₄Nb₆O₁₇/g-C₃N₄异质结

刘超^a^,^b^,^c, 封越^b, 韩字童^b, 孙耀^b, 王晓秋^c^,^d, 张勤芳^b^,^*(), 邹志刚^a^,^#()

^a南京大学环境材料与再生能源研究中心, 南京大学物理学院, 江苏南京210093
^b盐城工学院材料科学与工程学院, 江苏盐城224051
^c盐城工学院江苏省新型环保重点实验室, 江苏盐城224051
^d金陵科技学院理学院, 江苏南京211169

收稿日期:2020-02-26 接受日期:2020-04-09 出版日期:2021-01-18 发布日期:2021-01-18
通讯作者: 张勤芳,邹志刚
基金资助:
国家自然科学基金(51902282);国家自然科学基金(11474246);中国博士后科学基金(2018M632283);江苏省生态建材与环保装备协同创新中心暨江苏省新型环保重点实验室联合开放基金(JH201819);江苏省生态环境材料重点实验室开放课题

Z-scheme N-doped K₄Nb₆O₁₇/g-C₃N₄ heterojunction with superior visible-light-driven photocatalytic activity for organic pollutant removal and hydrogen production

Chao Liu^a^,^b^,^c, Yue Feng^b, Zitong Han^b, Yao Sun^b, Xiaoqiu Wang^c^,^d, Qinfang Zhang^b^,^*(), Zhigang Zou^a^,^#()

^aEcomaterials and Renewable Energy Research Center (ERERC), School of Physics, Nanjing University, Nanjing 210093, Jiangsu, China
^bSchool of Materials Engineering, Yancheng Institute of Technology, Yancheng 224051, Jiangsu, China
^cKey Laboratory for Advanced Technology in Environmental Protection of Jiangsu Province, Yancheng Institute of Technology, Yancheng 224051, Jiangsu, China
^dDepartment of Physics, Jinling Institute of Technology, Nanjing 211169, Jiangsu, China

Received:2020-02-26 Accepted:2020-04-09 Online:2021-01-18 Published:2021-01-18
Contact: Qinfang Zhang,Zhigang Zou
About author:^#Tel/Fax: +86-25-83686630; E-mail: zgzou@nju.edu.cn
^*Tel/Fax: +86-515-88298249; E-mail: qfangzhang@gmail.com;
Supported by:
National Natural Science Foundation of China(51902282);National Natural Science Foundation of China(11474246);China Postdoctoral Science Foundation(2018M632283);Joint Open Fund of Jiangsu Collaborative Innovation Center for Ecological Building Material and Environmental Protection Equipments and Key Laboratory for Advanced Technology in Environmental Protection of Jiangsu Province(JH201819);Open Project of Key Laboratory for Ecological-Environment Materials of Jiangsu Province

摘要/Abstract

摘要：

随着人口增长和全球工业化进程加快, 人们饱受环境污染和能源短缺问题的困扰. 半导体光催化技术作为一种高效、可持续、环境友好、有潜力的新技术, 在环境净化和能源开发方面有着广阔的应用前景. 到目前为止, 人们已开发出多种半导体光催化剂, 并广泛应用于污染物降解、氢气制备和二氧化碳还原等领域. 其中, 化合物K₄Nb₆O₁₇具有典型的层状结构、合适的电子能带结构、结构易改性以及良好的电荷传输性能等特点, 在光催化领域得到了广泛研究. 然而, 单纯K₄Nb₆O₁₇仍存在光响应范围窄、光生载流子复合率高等问题, 限制了K₄Nb₆O₁₇的进一步应用. 因此, 需要对K₄Nb₆O₁₇进行改性, 拓宽其光吸收范围, 提高其光生载流子分离效率, 从而提高其光催化活性.
本研究通过简单焙烧法制备Z型N-掺杂K₄Nb₆O₁₇/g-C₃N₄(KCN)异质结光催化剂, 其中石墨相氮化碳(g-C₃N₄)在复合材料中质量比约为50%. 层状K₄Nb₆O₁₇层板的电子结构通过N掺杂进行调控, 拓宽其光响应范围, 使其具有可见光响应; 同时, 形成的g-C₃N₄位于N-掺杂K₄Nb₆O₁₇的外层以及内层空间, 在这两种组分之间形成异质结, 有利于提高光生载流子的分离效率. 荧光光谱、时间分辨荧光光谱和光电化学测试表明, N掺杂和异质结的形成有利于增强光生电子-空穴对的传输和分离效率. 通过在可见光照射下降解罗丹明B(RhB)和产氢来评估材料的光催化性能. 相比g-C₃N₄ (8.24 µmol/h)和Me-K₄Nb₆O₁₇ (~1.30 µmol/h), KCN复合材料光催化产氢效率(~16.91 µmol/h)得到了极大提高, 并显示出极好的光催化产氢稳定性能. 对于光催化降解RhB体系, KCN复合材料也显示出较好的光催化活性和稳定性, 并能很好地将RhB矿化. 鉴于KCN复合材料具有较小的比表面积(9.9 m²/g)且无孔结构, 认为比表面积对光催化活性影响较小. 因此, 与单组分相比, KCN复合材料光催化产氢和RhB降解活性都得到了极大提高, 活性的增强主要归功于N掺杂和异质结形成的协同效应, 其中N掺杂可以拓宽光捕获能力, 异质结形成可提高电荷载流子的分离效率. 电子自旋共振(ESR)谱表明, 在KCN降解RhB体系中, 超氧自由基(•O₂^-)、羟基自由基(•OH)和空穴(h⁺)作为主要活性物质都参与了反应. 结合实验结果可以推测KCN复合材料满足了Z型光催化体系, 该体系具有高效的光生载流子分离效率和较高的氧化还原能力.

关键词: 光催化反应, K₄Nb₆O₁₇, g-C₃N₄, Z型光催化剂, 异质结

Abstract:

A simple calcination method was employed to prepare a Z-scheme N-doped K₄Nb₆O₁₇/g-C₃N₄ (KCN) heterojunction photocatalyst, in which the electronic structure of K₄Nb₆O₁₇ was regulated by N-doping, and g-C₃N₄ was formed both on the surface and within the interlayer spaces of K₄Nb₆O₁₇. The KCN composite showed profoundly improved photocatalytic activity for both H₂ generation and RhB degradation compared to its counterparts. This improved performance was attributed to the synergistic effects of N-doping, which broadened its light harvesting ability, and heterojunction formation, which increased the charge separation rate. The relatively low BET specific surface area of the KCN composite had little effect on its photocatalytic activity. Based on ESR spectroscopy studies, •O₂^-, •OH, and h ⁺ are the main active species in the photocatalytic degradation of RhB. Thus, it is reasonable to propose a Z-scheme photocatalytic mechanism over the KCN composite, which exhibits the dual advantages of efficient charge separation and high redox ability. Our work provides a simple approach for constructing large-scale Z-scheme heterojunction photocatalysts with high photocatalytic performance.

Key words: Photocatalysis, K₄Nb₆O₁₇, g-C₃N₄, Z-scheme, Heterojunction

刘超, 封越, 韩字童, 孙耀, 王晓秋, 张勤芳, 邹志刚. 高可见光催化降解污染物和产氢活性的Z型N-掺杂K₄Nb₆O₁₇/g-C₃N₄异质结[J]. 催化学报, 2021, 42(1): 164-174.

Chao Liu, Yue Feng, Zitong Han, Yao Sun, Xiaoqiu Wang, Qinfang Zhang, Zhigang Zou. Z-scheme N-doped K₄Nb₆O₁₇/g-C₃N₄ heterojunction with superior visible-light-driven photocatalytic activity for organic pollutant removal and hydrogen production[J]. Chinese Journal of Catalysis, 2021, 42(1): 164-174.

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图/表 9

Fig. 1. SEM images of (a) g-C3N4, (b) K4Nb6O17, and (c) the KCN composite. (d, e) TEM and (f, g) HRTEM images, and (h) EDS profile of the KCN composite. (i) STEM-HAADF image of the combined elements and (j-n) the distribution of the elements C/N/O/K/Nb on the KCN composite.

Fig. 2. (a) TG curves, (b) XRD patterns, and (c) UV-visible diffuse reflectance and (d) FT-IR spectra of the as-prepared samples.

Fig. 3. (a) XPS survey and XPS profiles of (b) Nb 3d, (c) O 1s, and (d) N 1s of the as-prepared samples.

Fig. 4. (a) Rate of H2 production on K4Nb6O17, Me-K4Nb6O17, g-C3N4, and KCN; (b) Cycling test of photocatalytic H2 production over the KCN composite under visible light. (Reaction conditions: 100 mg photocatalyst in 200 mL of an aqueous solution containing 10 vol% TEOA and 2 wt% Pt.)

Fig. 5. (a) Visible-light photocatalytic degradation rate of RhB solution over different samples. (b) UV-vis spectral changes. (c) TOC removal (relative to C0) and (d) photocatalytic degradation stability of RhB over KCN under visible-light irradiation.

Fig. 6. (a) PL spectra and (b) time-resolved PL decay spectra of the as-prepared samples.

Fig. 7. ESR spectra of a KCN dispersion in the dark and under visible light irradiation: (a) DMPO-?O2-, (b) DMPO-?OH, and (c) TEMPO-h+.

Fig. 8. (a) Transient photocurrent responses and (d) electrochemical impedance spectra of K4Nb6O17, Me-K4Nb6O17, g-C3N4, and the KCN composite.

Fig. 9. Schematic of the two possible photocatalytic mechanisms, i.e., the Z-scheme system and type-II heterojunction, for charge-transfer in the KCN composite under visible light. The energy levels of K4Nb6O17 and g-C3N4 in the KCN composite are referenced to the normal hydrogen electrode (NHE) at pH 7.

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高可见光催化降解污染物和产氢活性的Z型N-掺杂K₄Nb₆O₁₇/g-C₃N₄异质结

Z-scheme N-doped K₄Nb₆O₁₇/g-C₃N₄ heterojunction with superior visible-light-driven photocatalytic activity for organic pollutant removal and hydrogen production

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