MOFs自牺牲模板法制备CoNx/g-C3N4纳米材料用作高效光催化还原U(VI)

doi:10.15541/jim20210576

无机材料学报 ›› 2022, Vol. 37 ›› Issue (7): 741-749.DOI: 10.15541/jim20210576 CSTR: 32189.14.10.15541/jim20210576

所属专题：【能源环境】金属有机框架材料(202309)

MOFs自牺牲模板法制备CoN_x/g-C₃N₄纳米材料用作高效光催化还原U(VI)

洪佳辉(), 马冉, 仵云超, 文涛, 艾玥洁()

华北电力大学环境科学与工程学院, 资源环境系统优化教育部重点实验室, 北京 102206

收稿日期:2021-09-22 修回日期:2021-12-16 出版日期:2022-07-20 网络出版日期:2022-01-06
通讯作者: 艾玥洁, 副教授. E-mail: aiyuejie@ncepu.edu.cn
作者简介:洪佳辉(1997-), 女, 硕士研究生. E-mail: 136919867@qq.com
基金资助:
国家自然科学基金(22076044)

CoN_x/g-C₃N₄ Nanomaterials Preparation by MOFs Self-sacrificing Template Method for Efficient Photocatalytic Reduction of U(VI)

HONG Jiahui(), MA Ran, WU Yunchao, WEN Tao, AI Yuejie()

MOE Key Laboratory of Resources and Environmental Systems Optimization, College of Environmental Science and Engineering, North China Electric Power University, Beijing 102206, China

Received:2021-09-22 Revised:2021-12-16 Published:2022-07-20 Online:2022-01-06
Contact: AI Yuejie, associate professor. E-mail: aiyuejie@ncepu.edu.cn
About author:HONG Jiahui (1997-), female, Master candidate. E-mail: 136919867@qq.com
Supported by:
National Natural Science Foundation of China(22076044)

摘要/Abstract

摘要：

近年来, 利用石墨氮化碳(g-C₃N₄)光催化法将易溶的U(VI)还原为难溶的U(IV)来清除铀, 已逐渐成为放射性核素研究的热点。本研究将一种含金属钴的金属有机框架材料(MOFs)作为自牺牲模板, 利用简单热共聚法成功合成了含有Co-N_x构型的CoN_x/g-C₃N₄催化剂。在固液比为1.0 g/L、pH 5.0、可见光照射45 min下, 制备的催化剂(w(Co-MOFs) : w(g-C₃N₄)=1 : 1)对50 mg/L的U(VI)标准溶液还原率达到100%。从形貌, 微观结构和光学性能等方面对催化剂进行了表征,结果显示, 引入Co有效拓宽了g-C₃N₄对可见光的吸收范围, 抑制了光生电子与空穴的复合, 从而促进了U(VI)的还原反应。此外, 基于捕获实验深入探究了U(VI)在CoN_x/g-C₃N₄材料表面催化可能的反应机理。研究表明, CoN_x/g-C₃N₄复合光催化剂光学性能优异, 制备方法简单且绿色环保, 对放射性废水中的U(VI)的光催化还原去除效果较好。本工作对后续石墨氮化碳类新型材料的设计、合成与实际应用具有一定的参考作用。

关键词: 石墨氮化碳(g-C₃N₄), 金属有机框架材料(MOF), 光催化还原, 铀

Abstract:

Broad application of nuclear energy has resulted in the release of radionuclides such as uranium [U(VI)], into the environment, and its potential toxic and irreversible effects on the environment are among the paramount issues in nuclear energy use. Graphite carbon nitride (g-C₃N₄) is a kind of non-metallic material with the triazine structure. In recent years, the reduction of U(VI) to insoluble U(IV) by g-C₃N₄ photocatalysis has become a major research focus on the area of radioactive pollutants. In this work, a metal-organic framework (MOF) material containing cobalt metal was used as a self-sacrificial template. Through simple thermal copolymerization, the Co-N_x coordination was successfully incorporated into g-C₃N₄ to synthesize the CoN_x/g-C₃N₄ photocatalyst. The effects of the morphology, structure, and photoelectric properties of CoN_x/g-C₃N₄ on the photocatalytic reduction of U(VI) were investigated using macroscopic batch experiments. The results showed that the introduction of Co effectively broadened the absorption range of g-C₃N₄ to visible light, inhibited recombination of the photogenerated electrons and holes, and facilitated the reduction of U(VI). Under irradiation in visible light for 45 min, pH 5.0 and solid-liquid ratio of 1.0 g/L, the photocatalytic reduction of a standard 50 mg/L U(VI) solution reached 100% by CoN_x/g-C₃N₄(w(Co-MOFs) : w(g-C₃N₄)=1 : 1). Furthermore, the photocatalytic mechanism of CoN_x/g-C₃N₄ was investigated through capture experiments. In summary, the CoN_x/g-C₃N₄ composite exhibits excellent optical performance, has simple operation, is eco-friendly, and has a significant photocatalytic effect on U(VI) in radioactive wastewater. This work also provides design strategy and technical reference for applying g-C₃N₄ materials to treat radioactive wastewater.

Key words: graphite carbon nitride (g-C₃N₄), metal organic framework (MOF), photocatalytic reduction, uranium

中图分类号:

TQ174

洪佳辉, 马冉, 仵云超, 文涛, 艾玥洁. MOFs自牺牲模板法制备CoN_x/g-C₃N₄纳米材料用作高效光催化还原U(VI)[J]. 无机材料学报, 2022, 37(7): 741-749.

HONG Jiahui, MA Ran, WU Yunchao, WEN Tao, AI Yuejie. CoN_x/g-C₃N₄ Nanomaterials Preparation by MOFs Self-sacrificing Template Method for Efficient Photocatalytic Reduction of U(VI)[J]. Journal of Inorganic Materials, 2022, 37(7): 741-749.

图/表 6

图1 g-C3N4 (a)和CoNx/g-C3N4-1 (b)的SEM照片, (c) CoNx/g-C3N4-1的TEM照片和(d~f) CoNx/g-C3N4-1的C、N、Co元素分布图

Fig. 1 SEM images of (a) g-C3N4 and (b) CoNx/g-C3N4-1, (c) TEM images of CoNx/g-C3N4-1 and (d-f) elements distribution mappings of element C (red), N (blue), and Co (green) in CoNx/g-C3N4-1

图2 (a) g-C3N4和CoNx/g-C3N4的XRD谱图和(b) g-C3N4和CoNx/g-C3N4-1的N2吸附/脱附等温线及其比表面积

Fig. 2 (a) XRD patterns of g-C3N4 and CoNx/g-C3N4 and (b) N2 adsorption/desorption isotherms and corresponding specific surface areas of g-C3N4 and CoNx/g-C3N4-1

图3 CoNx/g-C3N4-1的(a) N1s, (b) C1s和(C) Co2p高分辨率XPS图谱

Fig. 3 High-resolution (a) N1s, (b) C1s and (c) Co2p XPS spectra of CoNx/g-C3N4

图4 g-C3N4和CoNx/g-C3N4-1光学性质与光电化学表征

Fig. 4 Optical properties and photoelectrochemical characterization of g-C3N4 and CoNx/g-C3N4-1 (a) UV-Vis diffuse reflectance spectra of g-C3N4 and CoNx/g-C3N4-1; (b) Plots of (αhʋ)1/2 versus energy (hʋ) for the band gap energies of g-C3N4 and CoNx/g-C3N4-1; (c) Time dependent photocurrent responses; (d) EIS Nyquist plots of g-C3N4 and CoNx/g-C3N4-1

图5 物理化学条件对CoNx/g-C3N4光还原U(VI)的影响(a~e);不同捕获条件下U(VI)浓度随时间变化的曲线(1.0 g/L CoNx/g-C3N4-1,pH 5.0,[U(VI)]=50 mg/L)(f)

Fig. 5 Influence of physico-chemical condition on photoreduction of U(VI) by CoNx/g-C3N4 (a-e), and curves of U(VI) changing with time under different capture conditions (1.0 g/L CoNx/g-C3N4-1, pH 5.0, [U(VI)]=50 mg/L) (f) (a) Influence of different catalysts(1.0 g/L catalysts, pH 5.0, [U(VI)]=50 mg/L); (b) Effect of pH (1.0 g/L CoNx/g-C3N4-1, [U(VI)]=50 mg/L); (c) Effect of solid-liquid ratio(CoNx/g-C3N4-1, [U(VI)]=50 mg/L, pH 5.0); (d) Effect of U(VI) concentration(1.0g /L CoNx/g-C3N4-1, pH 5.0); (e) Influence of different ionic strengths(1.0 g/L CoNx/g-C3N4-1, pH 5.0, [U(VI)]=50 mg/L)

图6 CoNx/g-C3N4光催化还原U(VI)的反应机理图

Fig. 6 Reaction mechanism for photocatalytic reduction of U(VI) with CoNx/g-C3N4

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MOFs自牺牲模板法制备CoN_x/g-C₃N₄纳米材料用作高效光催化还原U(VI)

CoN_x/g-C₃N₄ Nanomaterials Preparation by MOFs Self-sacrificing Template Method for Efficient Photocatalytic Reduction of U(VI)

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