ACS Applied Materials & Interfaces
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2019
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IF 8.456
Zhenyu Wang,Yu Huang,Meijuan Chen,Xianjin Shi,Yufei Zhang,Junji Cao,Wingkei Ho,Shun Cheng Lee
The development of catalysts that effectively activate target pollutants and promote their complete conversion is an admirable objective in the environmental photocatalysis field. In this work, graphitic carbon nitride (g-C3N4) microtubes with tunable N-vacancy concentrations were controllably fabricated using an in situ soft-chemical method. The morphological evolution of g-C3N4, from the bulk to the porous tubular architecture, is discussed in detail with the aid of time-resolved hydrothermal experiments. We found that the NO removal ratio and apparent reaction rate constant of the g-C3N4 microtubes were 1.8 and 2.6 times higher than those of pristine g-C3N4, respectively. By combining detailed experimental characterization and density functional theory calculations, the effects of N-vacancies in the g-C3N4 microtubes on O2 and NO adsorption activation, electron capture, and electronic structure were systematically investigated. These results demonstrate that surface N-vacancies act as specific sites for the adsorption activation of reactants and photoinduced electron capture, while enhancing the light-absorbing capability of g-C3N4. Moreover, the porous wall structures of the as-prepared g-C3N4 microtubes facilitate the diffusion of reactants, and their tubular architectures favor the oriented transfer of charge carriers. The intermediates formed during photocatalytic NO removal processes were identified by in situ diffuse reflectance infrared Fourier transform spectroscopy, and different reaction pathways over pristine and N-deficient g-C3N4 are proposed. This study provides a feasible strategy for air pollution control over g-C3N4 by introducing N-vacancy and porous tubular architecture simultaneously.
研究领域:
环境科学
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材料科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
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2024
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IF 8.1
Yu Zhang,Jingde Luan,Longde Jiang,Wengang Liu,Zheng Yan,Yu Bai
The enhanced driving force of charge carriers is crucial for improving the efficiency of photocatalytic hydrogen evolution of graphite carbon nitride (CN). N vacancy, grafted O and bridging C are successfully constructed to fabricate novel CN based photocatalyst (COV N @CN-20), using urea as precursor, maltodextrin as carbon and oxygen source via two-stage thermal polymerization. N vacancies serve as electron trap to providing more activation sites for hydroxyl and hydrogen ions. The surface grafted O becomes the electron enrichment center, providing electrons for hydrogen evolution reaction. The bridging C replaces the bridging N in the heptazine skeleton, enhancing the delocalized π state of electrons within the inner layer. The coupling effect of N vacancy, grafted O and bridging C facilitates band gap narrowing and promotes the efficient separation and migration of surface charge in COV N @CN-20. The experiments of photocatalytic hydrogen production indicate that the hydrogen yield of COV N @CN-20 reaches 1720.32 μmol g −1 without the need for any co-catalysts, 37.50 times than that of CN. The theoretical calculations indicate that the coupled surface-internal bridging engineering optimize its inherent electronic properties through surface defects, self-build-in electric field and electron enrichment, thereby improving carrier utilization for efficient hydrogen production.
研究领域:
材料科学
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能源化学
✓ 已验证
产品关联
DOI
高影响因子
APPLIED CATALYSIS B-ENVIRONMENTAL
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2021
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IF 19.503
Fang Li,Xiaoyang Yue,Dainan Zhang,Jiajie Fan,Quanjun Xiang
The excitons are known to exist in graphitic carbon nitride (g-C 3 N 4 ), but the contribution of excitons to the photocatalytic process has received only sporadic attention. Targeted regulation of excitons dissociation into free charges is an effective measure to improve the utilization of carriers and enhance photocatalytic activity. Here we designed the ultra-thin g-C 3 N 4 nanosheets modified with rich N vacancies (Nv-rich-CN) through molecular self-assembly and molecular intercalation strategies. N vacancies can effectively dissociate excitons into free charges. The electron concentration of the Nv-rich-CN is 3.24 times that of bulk g-C 3 N 4 (CN). Benefiting from the enhanced carrier utilization, Nv-rich-CN showed superior activity for CO 2 photoreduction under visible light irradiation. Femtosecond transient absorption spectroscopy revealed a photophysical model of exciton dissociation. Theoretical calculation results explained that the essential reason for the vacancy to promote exciton dissociation may be that the lack of local order provided a driving force for exciton dissociation. Besides, N vacancies acted as active sites in the process of CO 2 reduction, promoting the adsorption and activation of CO 2 by the photocatalyst. In situ diffuse reflectance infrared Fourier transform spectroscopy revealed the change of intermediate products during the reduction of CO 2 . This work focuses on the contribution of excitons in the photocatalytic process and provides a novel idea for enhancing the carrier utilization of photocatalysts.
研究领域:
材料科学
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光催化
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理论计算
✓ 已验证
产品关联
DOI
高影响因子
SCIENCE OF THE TOTAL ENVIRONMENT
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2020
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IF 6.551
Guanlong Wang,Ya Zhao,Huanran Ma,Chenjing Zhang,Xiaoli Dong,Xiufang Zhang
Constructing highly efficient metal-free material towards peroxymonosulfate (PMS) activation under photocatalytic assistance is a promising strategy for water decontamination . Herein, N vacancy modified g-C 3 N 4 nanotube (VCN) was prepared to build a novel photo-assisted PMS activation system (PPAS), in which the unique electronic structure created by N vacancy could favor the PMS activation on VCN under visible-light irradiation. The role of N vacancy in PPAS was firstly studied through tuning its content in VCN. The results showed that the N vacancy greatly improved PMS activation on VCN PPAS towards organic pollutants removal . The VCN PPAS with moderate N vacancy modification performed best, whose kinetic constant for Rhodamine B degradation was 9.6 and 2.6 times higher than that of VCN/PMS system and pristine g-C 3 N 4 PPAS, respectively. Moreover, the VCN PPAS performed well in wide pH range (3−12) and real water background. Selective removal of different organic pollutants was found on VCN PPAS, owing to the different interaction between pollutant and the catalyst surface with surface-bound radicals. The O 2 − and OH were major oxidants for pollutant removal in VCN PPAS, which were produced on dual active sites of VCN via two pathways: The N vacancy enhanced PMS adsorption and trapped photogenerated electrons for PMS reduction into OH, while the electron-deficient C atoms created by N loss promoted the PMS oxidation into O 2 − .
研究领域:
环境科学
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材料科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
SEPARATION AND PURIFICATION TECHNOLOGY
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2024
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IF 8.1
Yuyan Feng,Dongbo Wang,Qingge Feng,Chenghua Fan,Ying Lu,Wenqiang Yang
Activation of peroxymonosulfate (PMS) to generate reactive oxygen species (ROS) for pollutant degradation via metal-free photocatalysts is an important green wastewater treatment and remediation method, but the pathway for generating ROS via exciton effects in catalysts is often overlooked. In this study, OH/C=O co-modified N-defective rod-shaped carbon nitride (Nv-CN-O) was designed and synthesized by soft template and alkali hydrothermal method. In the Nv-CN-O/PMS/Light system, there was a synergistic degradation of tetracycline (TC) by carriers and excitons, with a degradation rate 2.15 times higher than that of CN/PMS/Light. N vacancies and OH/C=O enhanced the adsorption to PMS, accelerated the charge transfer process, and activated PMS to generate ·O 2 − dominated reactive species. The functional group OH/C=O promoted the production of triplet excitons that through the energy transfer pathway to promote the production of 1 O 2 . Abundant ROS were involved in the TC degradation process, and three possible TC degradation pathways were proposed. Nv-CN-O has strong anti-interference ability in actual water bodies, shows a promoting effect on the degradation of TC, which has practical application potential.
研究领域:
环境科学
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催化化学
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废水处理
✓ 已验证
产品关联
DOI
高影响因子
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