Nanoscale
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2016
·Vol. 8
·期 8
·4681-4687
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IF 7.76
Zexing Wu,Jie Wang,Lili Han,Ruoqian Lin,Hongfang Liu,Huolin L. Xin,Deli Wang
Investigating active, stable, and low-cost materials for the oxygen reduction reaction is one of the key challenges in fuel-cell research. In this work, we describe the formation of N-doped carbon shell coated Co@CoO nanoparticles supported on Vulcan XC-72 carbon materials (Co@CoO@N–C/C) based on a simple supramolecular gel-assisted method. The double-shelled Co@CoO@N–C/C core–shell nanoparticles exhibit superior electrocatalytic activities for the oxygen reduction reaction compared to N-doped carbon and cobalt oxides, demonstrating the synergistic effect of the hybrid nanomaterials. Notably, the Co@CoO@N–C/C nanoparticles give rise to a comparable four-electron selectivity, long-term stability, and high methanol tolerance; all show a multi-fold improvement over the commercial Pt/C catalyst. The progress is of great importance in exploring advanced non-precious metal-based electrocatalysts for fuel cell applications.
研究领域:
材料科学
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电化学
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能源研究
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FUEL
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2018
·
IF 4.908
Yang Zhou,Lu Li,Lijun Jin,Jian Zhou,Zhiwei Shi,Yang Li,Haoquan Hu
Coal pyrolysis is generally considered to initiate by cleavage of weak covalent bonds bridged between aromatic rings. The C–C covalent bonds are predominant bridged linkages among the framework of coal, which have a critical influence on coal pyrolysis reaction but lack of direct online observation. Five representative coal-related model compounds containing C–C bridged bonds, polypropylene (PP), polyvinylpyrrolidone (PVP), poly-4-vinylpyridine (P4VP), polystyrene (PS) and poly-4-vinylphenol, were selected to pyrolyze in an in-situ pyrolysis vacuum ultraviolet photoionization mass spectrometry (Py-VUV-PIMS). The soft ionized mass spectral detection can provide product distribution and evolved information of original products and intermediates, which are the key evidence to understand the initiation, recombination and reaction routes during pyrolysis process. Online analysis of pyrolysis reaction was found to be priority with cracking of C–C bond in the five polymer samples, and homologous free radicals and original products, which mainly include monomers, dimers and their alkyl and alkenyl radicals, were detected. The results reveal the cleavage temperature of C–C covalent bond is deeply related to its chemical environment, and obvious conjugation effect and steric effect for the bridged linkage were observed. In addition, the effect of hydrogen bond was also observed during the pyrolysis of model compounds containing hydroxyl groups, and intramolecular or intermolecular hydrogen bonding reduced the temperature at which C–C bridged bonds break. The analogous fracture mode and pyrolysis behavior of coal-related model compounds, which are beneficial to understand the reaction route and mechanism of coal pyrolysis, were discussed based on the experimental observations and theoretical calculation.
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ACS Omega
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2019
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IF 2.584
Jing Wang,Aisen Li,Shuping Xu,Chongping Song,Yijia Geng,Ling Ye,Houyu Zhang,Weiqing Xu
The mixed π–π packing of the donor (D) and acceptor (A) molecules is the highlighting feature of the intermolecular interactions following charge transfer (CT) issues in organic cocrystal systems. There is an inverse relationship between the D–A interplanar distance and the intermolecular CT interaction. However, the D–A C–C surface close contact (relative areas) on the intermolecular CT interactions in organic cocrystal systems is rarely investigated. Herein, we designed and constructed a novel cocrystal and its solvate cocrystal. The structural and electrostatic potential analyses suggest that the solvation destroys the N–H···N hydrogen bond interaction between phenothiazine (PTZ) and 1,2,4,5-tetracyanobenzene (TCNB), which causes the TCNB molecules to have a 90° rotation along the normal axis of the PTZ plane. Thus, the D–A C–C surface close contact is enlarged, strengthening the intermolecular π–π stacking interactions and intermolecular CT interaction between PTZ and TCNB, which are further evidenced by the absorption and Raman spectroscopic analyses. This study provides rare evidence of the enlarged C–C surface close contact in the mixed packing between D and A that greatly contributes to the intermolecular CT interaction in a D–A cocrystal system. It also provides a deeper understanding of the role of solvation in the structure–property relationship of organic cocrystal materials.
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Asian Journal of Organic Chemistry
·
2018
·Vol. 7
·期 10
·2039-2044
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IF 2.496
Qian-Qian Huang,Wei-Qiang Yu,Xiao-Lin Luo,Jin Gao,Jie Xu
Graphical An alternative method for glycerol hydrogenolysis to CH 4 and ethylene glycol that proceeds through preferential C−C bonds cleavage catalyzed by highly-dispersed Ru catalysts with tunable particle sizes via carbothermal reduction has been reported. An alternative method for the conversion of crude glycerol was proposed to produce renewable energy methane and high-value chemical ethylene glycol through preferential cleavage of C−C bonds, catalyzed by highly dispersed Ru-based catalysts prepared by carbothermal reduction. It was found that the Ru particles size could be tuned by adjusting the reduction temperature, and the size firstly decreased then increased with raising of the temperature of carbothermal reduction. This resulted in the opposite tendency of catalytic performance against the Ru particle sizes in hydrogenolysis of glycerol, in which the glycerol conversion and yield of C−C bond cleavage increased firstly and then decreased. Ru catalysts carbothermal reduced at 450 °C possessed highly dispersed Ru nanoparticles with uniform particle sizes about 1.0 nm that showed high hydrogenation activity and selectivity of C−C bond cleavage as well as good stability that could be recycled in aqueous phase hydrogenolysis of glycerol.
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ACS Catalysis
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2018
·
IF 11.384
Huifang Liu,Hongji Li,Jianmin Lu,Shu Zeng,Min Wang,Nengchao Luo,Shutao Xu,Feng Wang
Photocatalysis is a potentially promising approach to harvest aromatic compounds from lignin. However, the development of an active and selective solid photocatalyst is still challenging for lignin transformation under ambient conditions. We herein report a mild photocatalytic oxidative strategy for C–C bond cleavage of lignin β-O-4 and β-1 linkages using a mesoporous graphitic carbon nitride catalyst. Identifications by solid-state NMR techniques and density functional theory (DFT) calculations indicate that π–π stacking interactions are most likely present between the flexible carbon nitride surface and lignin model molecule. Besides, low charge recombination efficiency and high specific surface area (206.5 m2 g–1) of the catalyst also contribute to its high catalytic activity. Mechanistic investigations reveal that photogenerated holes, as the main active species, trigger the oxidation and C–C bond cleavage of lignin models. This study sheds light on the interaction between complex lignin structures and the catalyst surface and provides a new strategy of photocatalytic cleavage of lignin models with heterogeneous photocatalysts.
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Scientific Reports
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2017
·Vol. 7
·期 1
·1-10
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IF 4.259
Feng Shanglei,Yang Yingguo,Li Li,Zhang Dongsheng,Yang Xinmei,Xia Huihao,Yan Long,Tsang Derek K. L.,Huai Ping,Zhou Xingtai
An in-situ real-time synchrotron-based grazing incidence X-ray diffraction was systematically used to investigate the crystal structural evolution of carbon fiber reinforced carbon matrix (C/C) composite impregnated with FLiNaK molten salt during the heat-treatment process. It was found that the crystallographic thermal expansion and contraction rate of interlayer spacing d
002 in C/C composite with FLiNaK salt impregnation is smaller than that in the virgin sample, indicating the suppression on interlayer spacing from FLiNaK salt impregnated. Meanwhile the crystallite size L
C002 of C/C composite with FLiNaK salt impregnation is larger than the virgin one after whole heat treatment process, indicating that FLiNaK salt impregnation could facilitate the crystallization of C/C composite after heat treatment process. This improved crystallization in C/C composite with FLiNaK salt impregnation suggests the synthetic action of the salt squeeze effect on crooked carbon layer and the release of internal residual stress after heating-cooling process. Thus, the present study not only contribute to reveal the interaction mechanism between C/C composite and FLiNaK salt in high temperature environment, but also promote the design of safer and more reliable C/C composite materials for the next generation molten salt reactor.
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Catalysis Science & Technology
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2023
·Vol. 13
·期 6
·1748-1754
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IF 5
Shaoyuan Guo,Xinli Tong,Lingwu Meng,Guobao Yang
Selective oxidative C–C and C–O bond cleavage is of significance to the efficient utilization of biomass and biomass-derived platform compounds. In this work, the selective oxidative cleavage of C–C and C–O bonds has been developed with an iron-based catalyst (Fe–N–C) in the presence of molecular oxygen. Specifically, the β-O-4 lignin model compound was successfully converted to phenol and methyl benzoate in a methanol solvent, where the substrate conversion was 95.0% and the yields of phenol and methyl benzoate were 94.9% and 63.7%, respectively, when the reaction was performed with the Fe–N–C-850 catalyst at 120 °C for 4 h. Also, the oxidative transformations of other lignin models to phenols and methyl benzoates were achieved. Further investigations showed that the existence of the Fe3C phase in the catalyst plays an important role in the aerobic oxidative cleavage of C–C and C–O bonds in the β-O-4 lignin model.
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ACS Applied Materials & Interfaces
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2022
·
IF 10.383
Qifeng Chen,Guoming Gao,Huailin Fan,Jie Zheng,Lulu Ma,Yanyu Ding,Yanfen Fang,Ran Duan,Xiaofeng Cao,Yanchuan Guo,Dongge Ma,Xun Hu
The surface property of a photocatalyst, including surface acid sites and oxygen vacancies, plays a pivotal role in photocatalytic organic synthesis reactions. Benzoin isopropyl ether (BIE) is usually produced via polycondensation of benzaldehyde and catalyzed with highly toxic cyanide. Here, we report a green photocatalytic approach for the selective synthesis of BIE over WO3 driven by a green-light-emitting diode. The improved photocatalytic activity can be attributed to the synergy of oxygen vacancies (VOs) and acid sites over N-doped WO3 nanobelts. The results revealed that reactant molecules were predominantly adsorbed and activated on surface oxygen vacancies (VOSs) and the Brønsted acid promoted the etherification reaction; the introduction of VOs and nitrogen altered the band structure and electronic properties, resulting in improved photocatalytic activity. Our work provides an efficient approach to the selective photocatalytic synthesis of organics over photocatalysts with finely tuned surface properties and band structures via defect and doping engineering.
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CERAMICS INTERNATIONAL
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2022
·
IF 5.532
Ze Zhang,Cunqian Fang,Yuanqi Weng,Xiao Luo,Qizhong Huang,Huiping Hu
Graphene was introduced into C/C–SiC composites via pressureless impregnation to enhance the mechanical and thermal properties of the composites. The effects of various graphene contents on the mechanical and ablative performances of C/C–SiC composites were investigated. The results showed that the ultimate bending stress and compressive stress of the C/C–SiC composites increased by 28.98% and 23.64%, respectively, after adding 7.25% graphene. Moreover, the ablation rates of the composites were vastly decreased after adding a slight graphene content (2.13%). However, the ablation rates increased with increasing of graphene content, indicating that the benefit of introducing graphene on the ablation property decreased, which was mainly ascribed to the relative reduction in the SiC content. As a result, introducing slight graphene into C/C–SiC composites had the greatest benefit on the anti-ablation performance.
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ACS Applied Materials & Interfaces
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2020
·
IF 8.758
Xin-bo Xiong,Chun Liu,Xin-Ye Ni,Cai-qing Liang,Xie-rong Zeng
Hydroxyapatite (HA) coatings directly deposited by hydrothermal electrochemical technology (HET) onto carbon/carbon (C/C) composites exhibited a catastrophic failure occurring at the interface of the HA and C/C. To overcome this problem, a polyvinyl alcohol (PVA)/graphene oxide (GO) interlayer (P/G interlayer) was applied on the (NH4)2S2O8-pretreated C/C substrate (named P/G-C/C) by using a dipping method. Subsequently, a calcium phosphate coating was deposited on P/G-C/C, shortened as M-P/G-C/C, by HET, and then converted into HA coating (abbreviated as HA-P/G-C/C) through posthydrothermal treatment. For comparison, HA coating was prepared onto C/C without a P/G interlayer through the same process, which was denoted as HA-C/C. The composition, microstructure, and morphology of the samples were characterized by X-ray diffractometry (XRD), energy-dispersive spectroscopy (EDS), scanning electron microscopy (SEM), Raman spectra, Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS). The adhesive performance of the coatings on C/C was measured by a scratch test. Finally, an in vitro bioactivity of the coatings was evaluated in a simulated body fluid solution at 37 °C. Results showed no apparent differences in the morphology and phase of the posttreated coatings, both of which are composed of a dense structure containing needle-like HA crystals. However, the HA-P/G-C/C sample possessed a higher Ca/P ratio and denser interface, thereby exhibiting higher adhesive performance and better bioactivity. The adhesive strength of the HA-P/G coating was observed at a critical load of 41.04 N, which increased by 29.3% relative to the HA coating. Moreover, the failure site was on the HA-P/G coating rather than at the interface. The enhanced adhesive performance was ascribed to the PVA/GO-repairing pits on C/C and PVA and GO toughening effects on the HA coating. In vitro and in vivo tests revealed no statistical significance for the two HA-coated C/C samples, although the HA-P/G coating exhibited better bioactivity, inducing the growth of bonelike apatite than the HA coating.
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Molecular Catalysis
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2020
·
IF 3.687
Yang Zhong,Bo Zhou,Lijun Wang
Fe/FeO x embedded in LDH was prepared by reducing the pre-synthesized [Fe(C 2 O 4 ) 3 ] 3− anions intercalated LDH and used as a multi-functional catalyst for synthesis of C7-C9 compound via transfer hydrogenation between furfural (C5) and short-chain alcohols (C2-C4) and a subsequent aldol reaction of furfural with intermediate short-chain aldehydes in the absence of a homogeneous base with furfuryl alcohol as a byproduct. Screening reaction conditions, evaluation and improvement of the cyclic catalytic performance, and determination of catalytically active components were performed, and the results demonstrated that both high conversion and high selectivity to the C C bond forming product can be obtained under a non-oxidizing atmosphere of Ar or H 2 /Ar mixed gas, a reaction temperature of 140 °C and a reaction time of 4 h; the catalyst was easily deactivated during the cycle experiments, however, its catalytic stability can be effectively improved by depositing Ni with weak reducibility on the surface of Fe nanoparticles at the cost of reducing partial catalytic activity. Fe/FeO x together with LDH as a whole proved to be effective in catalyzing the transfer hydrogenation reaction and the support LDH imparted basic catalytic function to the composite realizing the aldol reaction in the absence of a homogeneous base.
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INDUSTRIAL CROPS AND PRODUCTS
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2024
·
IF 5.6
Zhen Huang,Penghao Sun,He Liu,Chunyu Ren,Xiangyu Lin,Minggui Shen,Zhaoshuang Li,Xu Xu
To obtain high-valued aromatic products, it is paramount to cleave the C α −C β bonds in lignin under mild conditions selectively. Nevertheless, this task remains daunting due to the formidable dissociation energies and steric hindrance associated with these bonds. Herein, a facile, efficient and cost-effective strategy for selectively breaking the C α −C β bond in lignin with visible-light irradiation and room temperature is proposed, facilitated by the utilization of the ferric-doped mesoporous graphitic carbon nitride (Fe/mpg-CN) photocatalyst. Collective contributed by the reduced band gap and photoluminescence, combined with intensified visible-light absorption and enhanced photocurrent, the effectiveness in photocatalytic activity of Fe/mpg-CN is offered. Specifically, a high conversion rate (98 %) of the lignin model compound (2-phenoxy-1-phenylethanol), coupled with an excellent selectivity of 98 % in cleaving the C α −C β bonds is achieved by Fe/mpg-CN. Photogenerated holes are indicated as the main active species through comprehensive mechanistic investigations. Additionally, the successful photocatalytic depolymerization of the complex dimer model compound (conversion rate ∼ 96 %) and pine kraft lignin further corroborate the satisfying photocatalytic activity and selectivity of Fe/mpg-CN. This study introduces a promising and viable strategy for the selective breaking of lignin through photocatalysis, offering significant implications for the sustainable production of valuable aromatic compounds.
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