2019 Vol. 34, No. 4

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2019, 34(4): .
Abstract(95) PDF(99)
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Research progress on the structure of graphene oxide
HUANG Man-hua, TANG Zhi-hong, YANG Jun-he
2019, 34(4): 307-314.
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The structure of graphene oxide (GO) is fundamental to understanding its properties and to realizing its applications. Experiment observations of the GO structure from different researchers are similar. However, the interpretation of the experimental data is still controversial due to the complicated oxygen functionalities and their arrangement. The Lerf-Klinowski structural model is one of the most popular used to fit experimental data and explain properties such as hydrophilicity and electrical resistivity. However, it has been challenged by new findings, and new structural models have been proposed in recent years. Based on the acidity of GO, Dimiev et al. proposed a dynamic structural model to explain the structure change of GO during its preparation and preservation in water. Rourke et al. proposed a two-component structural model to account for the acidification and oxidation behavior.
Efficient removal of organic dyes using a three-dimensional graphene aerogel with excellent recycling stability
DING Yue-ling, TIAN Zhen, LI Hui-jun, WANG Xiao-min
2019, 34(4): 315-324. doi: 10.1016/S1872-5805(19)60017-X
Abstract(356) PDF(205)
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The development of a renewable absorbent with a high adsorption efficiency is of great importance for the purification of dye wastewater. A nitrogen-doped graphene aerogel (N-GA) was prepared by a one-step hydrothermal and freeze-drying method using polyvinyl alcohol (PVA) as a cross-linking agent. Results indicated that the nitrogen doping provided more adsorption sites for the dyes. The PVA-N-GA showed excellent adsorption efficiencies for methylene blue (MB) (98.39% at pH=8) and methyl orange (MO) (78.78% at pH=2). The adsorption kinetic data of MB and MO on the PVA-N-GA were better fitted with a pseudo-second-order kinetic model than a pseudo-first-order kinetic model while the adsorption isotherms of MB and MO were better described by the monolayer Langmuir model and the multilayer Freundlich model, respectively. The PVA-N-GA showed excellent recycling stability with a negligible decay of adsorption efficiency after five cycles, which was ascribed to PVA making the three-dimensional (3D) pore structure of the N-GA more stable. The adsorption of the PVA-N-GA for dyes was mainly attributed to the π-π bonds, hydrogen bonds and electrostatic interactions.
Dynamic adsorption of ethyl acetate on adsorption beds filled with activated carbon fiber mesh and cloth
ZHOU Ping, ZHANG Zhong-liang, YOU Jun-qin, BAI Shu-pei, SONG Yan-long, HAN Hao, DONG Yan-chun
2019, 34(4): 325-332.
Abstract(334) PDF(62)
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The dynamic adsorption of ethyl acetate on two adsorption beds filled with (a) activated carbon fiber (ACF) mesh and (b) ACF cloth were investigated. The effects of gas velocity through the two beds on the pressure drop and breakthrough curves were compared. Results indicate that the pressure drop increases exponentially with the gas velocity and linearly with the filler thickness. The pressure drop of beds filled with the ACF mesh is only one thirtieth of that filled with the ACF cloth under the same gas velocity and filler thickness. The breakthrough curves were well fitted by the dynamic adsorption equation derived by Wheeler and modified by Jonas, from which the breakthrough time at a defined purification degree was obtained. The bed filled with the ACF mesh is superior to that filled with the ACF cloth in the purification of the volatile organic compounds at high gas velocities.
A multi-wall carbon nanotube/dithiothreitol interlayer to inhibit the shuttling of lithium polysulfides in a Li-S battery
WANG Jie, SUN Xiao-gang, LI Xu, CHEN Wei
2019, 34(4): 333-340.
Abstract(392) PDF(77)
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An interlayer made of a multi-wall carbon nanotube (MWCNT)/dithiothreitol (DTT) composite was placed between the positive electrode and the separator of a Li-S battery, where DDT was used as the reducing agent of lithium polysulfides, and MWCNTs as the reinforcement and diffusion barrier to inhibit the shuttling of lithium polysulfides. Results indicate that the formation of lithium polysulfides was inhibited and their diffusion to the negative electrode was reduced. The discharge capacity, utilization rate of the active substances, and rate and cycling performance of the Li-S battery were substantially improved. The initial discharge capacity of the battery was 1 674 mAh/g at 0.2 C and the utilization rate of active substances reached 99.9%. The initial discharge capacities were 1 094, 597 and 214 mAh/g at 1, 5 and 10 C, respectively. The discharge capacity was 780 mAh/g at 1 C after 300 cycles, which was 71.3% of its initial capacity.
Modification of a rice husk-based activated carbon by thermal treatment and its effect on its electrochemical performance as a supercapacitor electrode
XIAO Cheng-yuan, ZHANG Wen-li, LIN Hai-bo, TIAN Yong-xia, LI Xin-xin, TIAN Yi-ye, LU Hai-yan
2019, 34(4): 341-348. doi: 10.1016/S1872-5805(19)60018-1
Abstract(654) PDF(105)
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A hierarchically porous rice husk-based activated carbon, which had been prepared by a combined method (carbonization, NaOH-leaching and KOH activation), has a high specific capacitance and power density as a supercapacitor electrode in aqueous or organic electrolytes. It was subjected to a simple thermal treatment at 800℃ for 1 h to modify its microstructure and electrochemical performance. Results indicate that its original hierarchical pore structure is retained and the number of oxygen-containing functional groups is reduced after this modification. Mesopores developed and the volume ratio of mesopores to total pores increased from 25.62 to 33.62%. The modified activated carbon showed a higher specific capacitance of 147 F g-1 than the unmodified one (116 F g-1) at a current density of 0.5 A g-1. The voltage of the modified activated carbon was 84.5% of its initial value after self-discharge for 24 h, which is higher than that (75.2%) of the unmodified one. The capacitance retention of the modified carbon was 92% while that of the unmodified one was 85% after 10 000 galvanostatic charge/discharge cycles at 1 A g-1, indicating the better cycling stability of the former.
Synthesis and electrochemical performance of S/mesoporous carbon microsphere-MoS2 cathode materials
TAO Ying-qing, KONG Zhen-kai, WEI Yan-ju, WANG Ji-tong, QIAO Wen-ming, LING Li-cheng
2019, 34(4): 349-357.
Abstract(435) PDF(85)
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The commercial uses of Li-S batteries are still greatly limited by a number of obstacles such as the insulating nature of sulfur and its discharge products, the shuttling of intermediate polysulfides and the large volume change of sulfur during cycling. Here, we attached polar MoS2 to a well-developed mesoporous carbon microsphere (MCM) framework and used this as a highly efficient host for the sulfur cathode. Compared with a S/MCM cathode, the S/MCM-MoS2 cathode provided a higher discharge capacity, improved cycling stability and rate performance with an optimum MoS2 content of 12.4 wt.%. MoS2 is electrochemically active within the working voltage range of the sulfur cathode, which contributes extra capacity to the sulfur cathode with a stable cycling performance without loss of capacity in a 1 M LiTFSI electrolyte. The replacement of some of the electrochemically inactive carbon with MoS2 also increases the overall energy density. The exploration of such an electrochemically active host material may provide a new possibility for improving the electrochemical performance of Li-S batteries.
Fabrication and properties of graphene nanoribbon aerogels using Pickering emulsions as the template
HU Xiao-jing, ZHAO Zong-bin, LIU Yang, ZHAN Han, LIANG Jing-jing, QIU Jie-shan
2019, 34(4): 358-366.
Abstract(302) PDF(78)
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Graphene-based aerogels have attracted considerable attention because of their excellent properties, such as low density, high porosity, large specific surface area, and outstanding electrical conductivity, with promising use in the fields of sensors, catalysis, and energy-related storage. Here graphene nanoribbons were prepared by unzipping carbon nanotubes. Graphene nanoribbon aerogels were fabricated using Pickering emulsions as the soft template and poly(propylene glycol)bis(2-aminopropyl ether) (D400) as the co-surfactant and cross-linker. It was shown that aerogels prepared from an emulsion with a water/oil ratio of 7:1 have a uniform pore structure and excellent mechanical properties. The aerogels exhibit remarkable shape recovery after compression/release tests for 1 000 cycles at 50% strain. The structure can fully recover even after compression/release tests for 50 cycles at a 95% strain. The electrical conductivity of the aerogels is proportional to the strain regardless of the strain rate.
Effect of the CO2 activation parameters on the pore structure of silicon carbide-derived carbons
DUAN Li-qun, MA Qing-song, MA Lin-jian, DONG Lu, WANG Bo, DAI Xiao-qing, ZHANG Bo
2019, 34(4): 367-372. doi: 10.1016/S1872-5805(19)60019-3
Abstract(294) PDF(72)
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A silicon carbide derived carbon (SiC-DC) with a high specific surface area (SSA) fabricated by chlorination of a silicon carbide derived from polysiloxane was activated by CO2. The effect of activation temperature and time on the microstructure of the activated samples was investigated by N2 sorption, XRD, SEM and TEM. Results showed that CO2 activation effectively changed the pore structure of the SiC-DC and had little impact on carbon crystallinity. The activated samples retained the morphology of the SiC powder or the non-activated SiC-DC. The SSA, total pore volume (Vtot) and micropore volume of the activated SiC-DCs all increased and the yield decreased with increasing activation temperature or time. The SSA and Vtot increased by 46.5% (from 1 316.8 to 1 929.0 m2·g-1) and 86.4% (from 0.560 to 1.044 cm3·g-1), respectively after the SiC-DC was activated at 950℃ for 2 h, mainly as a result of the increased micropore volume.
The failure mechanism of a 2D-C/SiC panel structure under strong acoustic loading
LUAN Xin-gang, YIN Liang-xuan, CHEN Yu-tong, CHEN Bo, CHENG Lai-fei, LI Hai-bo, WU Zhen-qiang
2019, 34(4): 373-381.
Abstract(398) PDF(70)
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A 2D-C/SiC composite panel is used in the thermal protection system of a hypersonic vehicle that is exposed to a combination of high force and temperature. Such an environment has a serious effect on the performance and structural dynamics of the panel. An acoustic test with an intensity ranging from 156 to 165 dB was carried out on a 2D-C/SiC panel. Its morphology before and after the test was obtained by infrared thermal imaging. The fracture morphology and the initiation and propagation positions of cracks were observed by SEM, and the failure mechanism of the 2D-C/SiC panel under strong acoustic loading was revealed. The composite panel showed fatigue failure caused by a combination of high frequency stretching and out-of-plane shearing. The former caused pull-out of carbon fibers and their brittle failure while the latter contributed to the rapid propagation of cracks.
Preparation and antibacterial activities of copper nanoparticles encapsulated by carbon
CHEN Hai-feng, WU Juan-juan, WU Ming-yue, JIA Hui
2019, 34(4): 382-389. doi: 10.1016/S1872-5805(19)60020-X
Abstract(477) PDF(89)
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Copper nanoparticles encapsulated by carbon (Cu-NPs@C) were synthesized by a two-step method by mixing cupric chloride and glucose in a solution, followed by carbonization. The microstructures and antibacterial activities of the Cu-NPs@C samples were characterized by TEM, XRD, XPS, nitrogen adsorption and antibacterial activity tests. Results indicated that the as-synthesized Cu-NPs had a FCC crystal structure and a spherical morphology of diameter 4-46 nm and were well dispersed in the porous graphitic carbon layers. When the mass ratio of cupric chloride to glucose was less than 1:5, the Cu-NPs@C were of pure metallic copper without any oxides, and were stable against ambient air oxidation. The Cu-NPs@C synthesized with a mass ratio of cupric chloride to glucose of 1:5 had a specific surface area of 418 m2/g, which showed much higher antibacterial activities against three different common bacteria (Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa) than pure nano-copper powder. It was believed that the carbon layers are responsible for capturing the bacteria while the copper ions released from the copper nanoparticles kill them. The outer carbon layers effectively protected the metallic copper inside from oxidation. These findings indicate that Cu-NPs@C can be used as a stable antibacterial agent in biomedical applications.
Preparation of nitrogen-doped carbon dots with a high fluorescence quantum yield for the highly sensitive detection of Cu2+ ions, drawing anti-counterfeit patterns and imaging live cells
LIU Wen, ZHANG Rong, KANG Yu, ZHANG Xiao-ying, WANG Hao-jiang, LI Li-hong, DIAO Hai-peng, WEI Wen-long
2019, 34(4): 390-402. doi: 10.1016/S1872-5805(19)60021-1
Abstract(374) PDF(86)
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Water-soluble luminescent nitrogen-doped CDs (N-CDs) having a high QY of 29.83% were prepared by a one-step microwave-assisted pyrolysis method using ammonium citrate and triethylenetetramine as the precursors. The microstructure, optical properties and biocompatibility of the N-CDs were investigated. Results indicate that they exhibit a strong fluorescence, favorable biocompatibility and excellent optical stability. Their photoluminescence is quenched by Cu2+ ions through the formation of a complex between the N-CDs and Cu2+, which can be used for Cu2+ detection. Compared with other CD-based nanomaterials, the N-CDs show outstanding optical properties, and excellent selectivity and sensitivity for Cu2+ detection with a linear range of 0.01-11 μM and a detection limit of 4.5 nM. The selectivity for Cu2+ detection is so good that the N-CDs have been successfully used in Cu2+ detection for real water samples. They have also been used to draw fluorescent patterns and image living cells.

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