Journal of Materials Chemistry C
·
2019
·Vol. 8
·期 4
·1286-1291
·
IF 6.641
Xiaoxi Li,Zifei Wang,Yang Liu,Weiguang Zhang,Chaofeng Zhu,Xiangeng Meng
Fluorescent carbon dots (CDs) have emerged as promising materials for white light-emitting diodes (WLEDs) on account of carbon's intrinsic merits of high stability, low cost, and environment-friendliness. However, CDs usually give relatively narrow emission with full width at half maximum within 70–90 nm, which fundamentally restrains construction of CDs-based WLEDs with high color rendering index (CRI). Here, we demonstrate tricolor ultrabroad-band (109–120 nm) emissive CDs (Tri-CDs) with a quantum yield (QY) up to 21–64% by a one-pot solvothermal route. Experimental investigations reveal that tunable emissions of these CDs are based on differently sized sp2 conjugated domains and the content of graphitic nitrogen, which can be modulated by controlling the carbonization and deamination processes during solvothermal reactions. The ultrabroad-band emission spectra of Tri-CDs originate from broad distribution of the particle size. A WLED with Commission Internationale de l’Eclairage (CIE) color coordinate of (0.362, 0.370) and high CRI of 96.5 is fabricated by integrating Tri-CDs films with an ultraviolet LED chip. This work opens up a new opportunity for the development of high CRI CDs-based WLEDs.
研究领域:
材料科学
·
光学工程
✓ 已验证
DOI
高影响因子
APPLIED SURFACE SCIENCE
·
2016
·
IF 3.15
Kui Li,Feng-Yun Su,Wei-De Zhang
Carbon quantum dots (CQDs) were deposited onto graphite-like carbon nitride nanosheets (CNNS) to form CNNS/CQDs composites. The prepared CNNS/CQDs composites exhibit much higher photocatalytic activity under visible light irradiation than pure CNNS do. The CNNS/CQDs-7 sample displays the highest photocatalytic performance, with H 2 production rate of 116.1 μmol h −1 , which is three times of that over pure CNNS (37.8 μmol h −1 ). Photoluminescence spectroscopy and photoelectrochemical (PEC) analysis reveal that the CQDs are favorable for trapping electrons and promoting the separation of photogenerated electron-hole pairs in CNNS. A possible photocatalytic mechanism of the enhanced photocatalytic performance for H 2 generation over CNNS/CQDs will be proposed in this paper.
研究领域:
材料科学
·
能源科学
✓ 已验证
产品关联
DOI
高影响因子
Reaction Kinetics Mechanisms and Catalysis
·
2020
·Vol. 129
·期 2
·865-881
·
IF 1.52
Liu Minjie,Zhang Hao,Wang Junyan,Zhao Guoming,Liu Di
A Co–N–C catalyst was fabricated via pyrolysis–reduction process. Dehydrogenation/hydrogenation and base catalysis performances of the Co–N–C catalyst were investigated by using the reductive coupling of nitroarenes with alcohols and aldol condensation as probe reactions. Various characterizations were performed to explore effects of reduction and pyrolysis temperature on the structure/composition and basicity of the Co–N–C catalyst, and the relationship between structure-dehydrogenation/hydrogenation and base catalysis performance was discussed accordingly. Two different structures of Co–N–C catalyst (Co–N–C/C 3 N 4 and Co–N–C/CNT) were obtained in different pyrolysis temperature. Co–N–C-600 with C 3 N 4 exhibits very weak catalytic performance owe to its poor pore system and active phase. Dehydrogenation/hydrogenation behaviors of Co–N–C/CNT depend on the amount of Co–N, graphitic N in Co–N–C, while the basicity of Co–N–C is closely related to the content of N species, particularly pyrrolic N and pyridinic N. The appropriate pyrolysis temperature benefits the formation of active species, developed pore organization and strong basicity. And, the H 2 reduction improve dehydrogenation/hydrogenation activity of Co–N–C/CNT because reduction can destroy carbon coating layers to expose more Co–N species and promote the transformation of N species to graphitic N. Meanwhile, H 2 reduction increases the contents of graphitic N and reduces the content of pyrrolic N and pyridinic N, thus weakening catalyst basicity and consequently reducing base catalytic activity of Co–N–C/CNT.
研究领域:
化学
·
催化材料科学
✓ 已验证
产品关联
DOI
高影响因子
DYES AND PIGMENTS
·
2020
·
IF 4.613
Changqing Ye,Lei Xu,Shuoran Chen,Caihong Wang,Meng Su,Guoliang Dai,Xiaomei Wang,Fengyu Li,Yanlin Song
Carbon dots ( CD s) with controllable excitation-dependent fluorescence ( EDFL ) were elaborately prepared for the application of multiplex metal ion discrimination. A serial of CD samples were synthesized through a simple solvothermal reaction in which extra nitrogen sources with enhancing chemical reducibility were added into a specific nitrogen-contained precursor. Both experimental characterizations and theoretical calculations based on density functional theory have proved that the functional group of graphitic nitrogen ( GN ) is the key factor to achieve EDFL , and the content of GN was determined by the reducibility strength of extra nitrogen sources in the synthesis. In that case, sensing channels with different response behaviours to multiplex analytes can be formed due to the controllable EDFL of CD s. As a result, seventeen types of metal ions can be detected and recognized through the as-prepared CD probes. This work provides a novel angle to understand and engineer the EDFL property of CD s, as well as a facile strategy to appropriately construct high effective sensing channels for multi-analyte detection.
研究领域:
材料科学
·
分析化学
✓ 已验证
产品关联
DOI
高影响因子
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
·
2023
·
IF 7.2
Jun Shi,Xiaoshan Zhang,Sabarinathan Ravichandran,Shirong Sun,Yulong Li,Ruoyu Wu,Wanxuan Luo,Hongmei Xing,Wenli Zhang
We report here the synthesis of N-doped porous carbon (PC) through a convenient melamine pre-grafting strategy. The melamine derivative with a monolayer structure was first grafted on the surface of the micropores of PC using a suitable diazotization reaction of melamine in an aqueous solution. After pyrolysis , PC grafting with melamine derivative was converted to the obtained N-doped PC. Meanwhile, more nitrogen dopants were grafted, and nitrogen functionalities were reconstructed to generate more graphitic N and pyridinic N atoms, in which the mesopores volume was consequently enlarged. Because of the unique structures mentioned above, the as-obtained N-doped PC exhibited enhanced oxygen reduction activity under alkaline compared with the N-doped PC from the standard physical mixture of PC and melamine. Besides, the obtained N-doped PC showed a comparable half-wave potential, remarkable durability, and good methanol tolerance compared with the commercial 20% Pt/C electrocatalyst . The results presented here could guide the development of new and improving metal-free nitrogen-doped porous carbon catalysts toward oxygen reduction reaction.
研究领域:
材料科学
·
电化学
✓ 已验证
产品关联
DOI
高影响因子
ACS Applied Nano Materials
·
2025
·
IF 5.5
Pengxuan Wu,Wanbing Ma,Yuxin Ge,Jinbao Xu,Minglei Lu,Xia Li,Liang Ma,Song Bai,Tiejun Wang
A facile one-step method was developed to promote the carbon dioxide reduction reaction (CRR) activities to form the C2 products (C2H4 and C2H5OH) via the capping agent and organic solvent-free involvement of copper (Cu) on graphitic carbon nitride (GCN). By tuning the using amount of the Cu precursor, Cu-GCN-0.2 exhibited a total Faradaic efficiency (FE) of more than 86.69 ± 0.73% for the C1 species (CO, CH4, HCOOH) and C2 species (C2H5OH, C2H4) as the CRR products when the electrolysis was carried out at an overpotential of 0.7 V (vs RHE) even after 12 h electrocatalysis and at a ratio of about 1:1 for C2/C1. Further investigation confirms that the enhanced CRR activities can be ascribed to three aspects: Firstl’y, smartl’y regulation of the Cu involvement during the synthesis of GCN created the CRR active site, which enables more CO2 to be adsorbed and activated at a lower overpotential to participate in the C–C couple procedures. Secondly, the neglected HER active site was formed when Cu was involved, which enables the well-maintained proton generation and adsorption activities for the proton-coupled electron transfer procedures, leading to the promoted C2/C1 ratio. Thirdly, the decreased electronic resistance accelerates the electronic transfer speed, which enables a faster reaction rate and a promoted long-term durability performance. This research provides a facile method for the rational construction and preparation of the electrocatalyst toward large-scale utilization in sustainable conversion and application.
研究领域:
材料科学
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电化学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF THE ELECTROCHEMICAL SOCIETY
·
2023
·Vol. 170
·期 11
·114502
·
IF 3.9
Rizwan Haider,Yi Wan,Yu Huang,Ayaz Muzammil,Renhuan Li,Muhammad Zahid,Asif Mahmood,Yi Fan,Xianxia Yuan
Hollow nitrogen-doped carbons, a class of metal free electrocatalysts, offer a wide range of modifications due to their tunable diameter and carbon wall thickness. Herein, hollow nitrogen-doped carbon spheres (HNCS-1000) with numerous structural defects, thin carbon wall of about 8 nm, high (sp2-sp3)/sp3 bond ratio of 3.11 and graphitic-N proportion of 71.4% are prepared using a double pyrolysis strategy. When employed as ORR catalyst in O2-saturated 0.1 M KOH solution, HNCS-1000 retains high onset and halfwave potentials of 1.03 V and 0.88 V, respectively. In addition, it also demonstrates excellent stability/durability with 90.25% current density retention after 84000 s continuous chronoamperometric operation and only 33 mV loss in halfwave potential after 7000 CV cycles. Overall, the ORR performance of HNCS-1000 surpasses most of the previously reported nitrogen-doped carbon catalysts, and it is among the best catalysts for ORR in alkaline environment.
研究领域:
材料科学
·
电化学
✓ 已验证
DOI
高影响因子
CATALYSIS TODAY
·
2024
·
IF 5.2
Wei Lv,Yao Wang,Hong Chen,Yongqi Tang,Yongdan Li
Nitrogen atom-doped biomass carbon prepared from corn stover is a newly discovered metal-free catalyst that shows good activity on the selective oxidation of 5-hydroxymethylfurfural (5-HMF) to 2,5-diformylfuran (DFF). Here, the presence of graphitic nitrogen on the catalyst surface activated the oxygen adsorbed on the carbon sites next to the graphitic nitrogen in the carbon material and promoted the formation of oxygen radicals on the surface-active sites, improving the HMF oxidation process. The results show that the catalyst NC-800 reacted with acetonitrile as the reaction solvent at 110 °C and 1.0 MPa O 2 for 8 h to obtain 93.0 % HMF conversion and 94.4 % DFF selectivity, and the 5-HMF conversion and DFF selectivity were maintained at more than 85 % after five cyclic tests, with excellent cyclic stability. One of the main factors influencing the material flaws is the variation in pyrolysis temperature. Using maize stover, a readily available and renewable biomass, in the catalytic oxidation of biomass platform compounds may improve biomass utilization more extensively.
研究领域:
生物质能
·
催化化学
✓ 已验证
产品关联
DOI
高影响因子
Materials Research Express
·
2021
·Vol. 8
·期 5
·055504
·
IF 1.62
Fengpo Yan,Hao Zhang,Yu Zhang,Fugui Yang
0.3 mol% platinum loaded g-C3N4 sample was prepared by photoreduction method to study the long-term stability of photocatalysts. For the first time, we have discovered the oriented attachment (OA) mechanism growth of Pt nanoparticles on g-C3N4 solid surface, which is completely different from Ostwald ripening (OR) or particle migration and coalescence (PMC) that previously reported. The Pt nanoparticles perform Brownian motion on the surface of g-C3N4 support under the collision of liquid molecules, then two or more nanoparticles attach together via the crystallographic orientation to construct larger ones. Al2O3 film prepared by atomic layer depositon was introduced to inhibit the Brownian motion of Pt nanoparticles. It is found that as the increase of the Al2O3 growth cycles, the photocatalytic hydrogen production of Pt/g-C3N4 coated by Al2O3 increase from 1.14 mmolg−1h−1 to 2.08 mmolg−1h−1 and then decrease to 1.4 mmolg−1h−1, and the apparent quantum efficiency (QE) also increase from 1.2% to 2.1% and then decrease to 1.4%. Meanwhile, the long-term stability of photocatalyst always increases. This work has revealed new pathway of photocatalytic nanoparticle growth on solid surface and proposed the method to prevent it.
研究领域:
材料科学
·
光催化
✓ 已验证
DOI
高影响因子
JOURNAL OF ELECTROANALYTICAL CHEMISTRY
·
2018
·
IF 3.235
Anran Liu,Mengyao Ma,Xiaoqin Zhang,Jing Ming,Ling Jiang,Ying Li,Yuanjian Zhang,Songqin Liu
Nitrogen doped carbon nanomaterials are excellent electrode materials and catalysts due to their extraordinary conductivity, prolific structures, and abundant active sites. Herein, two kinds of waste biomass, catkins and Okara were used as precursors for the preparation of novel nitrogen doped carbon fibers via hydrothermal and pyrolysis process . The blend of nitrogen-rich Okara with catkins effectively enhanced the content of doped nitrogen in the product. The as-prepared sample (denoted as NCF900) exhibited a hollow fiber like structure with a diameter of 2 to 5 μm and had abundant highly active sites of pyridinic N and graphitic N, thereby improving its electrocatalytic activity in oxygen reduction reaction (ORR). The typical rotating disk electrode test proved that the NCF900 exhibited a high onset potential (0.82 V vs RHE) and a nearly four-electron pathway for ORR in alkaline solution as well as stronger methanol tolerance and better long-term durability than commercial Pt/C. The green, low cost synthetic method and the excellent ORR catalytic efficiency of NCF900 made it a promising electrocatalytic material for the ORR in fuel cells.
研究领域:
材料科学
·
能源科学
·
环境科学
✓ 已验证
DOI
高影响因子
Nanoscale
·
2020
·Vol. 12
·期 9
·5543-5553
·
IF 6.895
Shihong Wu,Ronghui Zhou,Hanjiao Chen,Jinyi Zhang,Peng Wu
Photosensitization is a promising avenue of oxygen activation, which can overcome the spin selection rule to transform the ground state oxygen (3O2) into a highly reactive singlet oxygen (1O2). Carbon dots (CDs) are a promising type of carbon-based photosensitizer, and nitrogen doping can further improve the oxygen photosensitization performance. Although the roles of nitrogen doping in tuning the optical properties (mainly absorption and fluorescence) of CDs have been well-studied, their association with oxygen photosensitization has not been reported. Herein, using the well-developed synthetic protocol of hydrothermal treatment of citric acid and ethylenediamine, we prepared nitrogen-doped CDs (N-CDs) of varied nitrogen contents. The oxygen photosensitization performances of the N-CDs were first confirmed by ROS investigation with TMB oxidation as the ROS probe and EPR. After XPS analysis of the surface nitrogen doping speciation, it was found that the changes of graphitic N and pyrrolic N correlated well with the oxygen photosensitization performances of N-CDs. Further theoretical calculations indicated that the two key factors for oxygen photosensitization, namely triplet activation and oxygen adsorption, are mainly associated with graphitic N and pyrrolic N, respectively. The results in this work help further understanding of the oxygen photosensitization mechanism of N-CDs, and are expected to be useful in the future design of carbon-based photosensitizers.
研究领域:
材料科学
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光化学
·
环境科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
GREEN CHEMISTRY
·
2016
·Vol. 18
·期 15
·4254-4262
·
IF 8.506
Fan Yang,Cheng Chi,Chunxia Wang,Ying Wang,Yongfeng Li
Four kinds of nitrogen-doped graphene (NG) as metal-free catalysts are synthesized by a one-step hydrothermal reaction and thermal treatment using graphene oxide and urea as precursors. It is found that the reduction of nitroarenes can be catalyzed by using a low NG loading and a small amount of NaBH4 in water with high yield. The type of nitrogen species in NG has an important effect on the reduction reaction. The NG catalyst containing the most graphite N shows the highest catalytic activity during reduction of nitroarenes, which demonstrates that the graphite N of NG plays a key role in impelling this reaction. The reaction mechanism is proven by GC-MS experiments, and DFT calculations reveal the reasons for the graphite N showing better catalytic activity. It is worth noting that no dehalogenation phenomenon occurs during the reduction process for halogen-substituted nitroarenes in contrast to conventional metal catalysts. In addition, the NG catalyst can be simply recycled and efficiently used for eight consecutive runs with no significant decrease in activity.
研究领域:
材料科学
·
催化化学
·
环境科学
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）