2017 Vol. 32, No. 4

Graphical Contents
2017, 32(4): .
Abstract(226) PDF(404)
Abstract:
A one-step hard-templating method for the preparation of a hierarchical microporous-mesoporous carbon for lithium-sulfur batteries
NIU Shu-zhang, WU Si-da, LU Wei, YANG Quan-hong, KANG Fei-yu
2017, 32(4): 289-296. doi: 10.1016/S1872-5805(17)60123-9
Abstract(465) PDF(602)
Abstract:
Porous carbon materials can increase the conductivity of sulfur and restrain the shuttling of polysulfides in the electrolyte. A hierarchical microporous-mesoporous carbon (HMMC) with a large surface area and pore volume was prepared by the simple one-step carbonization of a mixture of magnesium gluconate (MG) and phenolic resin. The MG was transformed into nanosize magnesium oxide that acted as a hard template during carbonization to create mesopores. The HMMC has a high surface area (~1 560 m2·g-1) and large pore volume (~2.6 cm3·g-1), which provides abundant space for sulfur loading and accommodates volume changes during charge/discharge. The interconnected pore structure and carbon framework ensure fast electron and Li ion transfer. As the cathode of a Li-S battery the sulfur-loaded HMMC has a high discharge capacity of 939 mAh·g-1 at 0.3 C and a reversible capacity of 731 mAh·g-1 after 150 cycles with only a 0.15% capacity fade per cycle. Even at a high rate of 2 C, it still delivers a high discharge capacity of 626 mAh·g-1, showing an excellent rate performance.
N-doped hollow carbon nanospheres as sulfur hosts for high performance Li-S batteries
ZHANG Yong-zheng, DING Li-xin, ZHAN Liang, WANG Yan-li, SONG Yan
2017, 32(4): 297-303.
Abstract(475) PDF(540)
Abstract:
SiO2@C nanospheres were fabricated by polymerization of dopamine in the presence of tetraethyl orthosilicate followed by carbonization and the SiO2 was chemically etched away to obtain hollow N-doped carbon nanospheres (N-CNs) to host sulfur. The resulting material (S@N-CNs) was used as the cathode material of a Li-S battery. Results indicate that the S@N-CNs can effectively suppress the volume expansion of sulfur and the shuttle effect of polysulfides during charge and discharge. Nitrogen doping improves the electrical conductivity of the N-CNs. The initial reversible capacity of the S@N-CN electrode at 0.2 C is 1 179 mAh·g-1, which remains at 540 mAh·g-1 after 100 cycles. The electrode has excellent rate capability (343 mAh·g-1 at 1 C and 247 mAh·g-1 at 2 C).
Preparation and electrochemical properties of NaF-Si-C-RGO hybrids
LI Xiao, SONG Yan, TIAN Xiao-dong, WANG Kai, GUO Quan-gui, LIU Lang, CHEN Cheng-meng
2017, 32(4): 304-310.
Abstract(394) PDF(423)
Abstract:
NaF and Si nanoparticles and graphite oxide (GO) flakes were dispersed in a thermosetting phenolic resin (PR) in an aqueous solution, followed by drying and carbonization at 700℃ to produce NaF-Si-C-RGO hybrids. The structure of the hybrids was characterized by SEM, TEM, TGA, XRD and Raman spectroscopy. The electrochemical properties of the hybrids as anode materials of lithium ion battery were investigated and showed better electrochemical performance, larger reversible capacity and higher capacity retention when compared with both NaF-Si-RGO and Si-C-RGO hybrids. The amorphous carbon coating on the Si nanoparticles, derived from the PR, restricts the formation of a solid-electrolyte interface film. The Na+ in NaF is inserted between the GO layers, which not only alleviates the re-stacking of graphene sheets, but also improves the dispersion of Si nanoparticles in RGO layers, leading to a high utilization of active materials. F-also inhibits the decomposition of the electrolyte and the generation of HF, which is favorable for the cycle stability of the electrode.
Synthesis of SiO2@carbon-graphene hybrids as anode materials of lithium-ion batteries
YIN Ling-hong, WU Ming-bo, LI Yan-peng, WU Gui-liang, WANG Yuan-kun, WANG Yang
2017, 32(4): 311-318. doi: 10.1016/S1872-5805(17)60124-0
Abstract(482) PDF(457)
Abstract:
SiO2@carbon-graphene (SiO2@C-G) hybrids with excellent electrochemical performance were prepared by the self-assembly of colloidal silica, sucrose and graphene oxide followed by ultrasonic-assisted hydrothermal and heat treatments. The mass ratio of silica to sucrose is crucial to the electrochemical performance of the resulting hybrids. A hybrid with a mass ratio of silica to sucrose of 0.15 shows the best reversible lithium storage performance, delivering an initial discharge capacity of 906 mAh·g-1 and a capacity of 542 mAh·g-1 at the 216th cycle at a current density of 100 mA·g-1. The excellent cycling ability and high reversible capacity are attributed to a synergetic effect of the good conductivity of the SiO2@C-G hybrids, the small SiO2 particle size and the good dispersion of SiO2 nanoparticles in the hybrids. This methodology may provide a simple, scalable and eco-friendly strategy to prepare superior electrode materials from cheap and low electrical conductivity metal oxides.
Wood-based activated carbons for supercapacitor electrodes with a sulfuric acid electrolyte
Aleksandrs Volperts, Galina Dobele, Aivars Zhurinsh, Darya Vervikishko, Evgeny Shkolnikov, Jurijs Ozolinsh
2017, 32(4): 319-326. doi: 10.1016/S1872-5805(17)60125-2
Abstract(407) PDF(372)
Abstract:
Wood-based activated carbons were synthesized in a two-stage thermochemical process using sodium hydroxide as an activator, and used as the electrode materials for supercapacitors with a sulfuric acid electrolyte. The dependence of pore structure parameters and the electrochemical properties of the activated carbons on the synthesis conditions was investigated. Results indicate that an electric double layer is formed within micropores while meso and macropores are responsible for ion transport. Excess activation under a high activation temperature and/or a high mass ratio of sodium hydroxide to carbonaceous material leads to high meso and macropore volumes, which increase electrolyte uptake and therefore decrease the specific capacitance based on cell mass. The optimum activated carbon is obtained at an activation temperature of 600℃ with a mass ratio of sodium hydroxide to carbonaceous material of 1.25.
Synthesis of multicolor photoluminescent carbon quantum dots functionalized with hydrocarbons of different chain lengths
Kayo Oliveira Vieira, Jefferson Bettini, Luiz Fernando Cappa de Oliveira, Jefferson Luis Ferrari, Marco Antonio Schiavon
2017, 32(4): 327-337. doi: 10.1016/S1872-5805(17)60126-4
Abstract(616) PDF(338)
Abstract:
We report the synthesis of novel multicolor photoluminescent carbon quantum dots (CQDs) from multi-wall carbon nanotubes, and their covalent functionalization with amines by peptide bonds. The resulting CQDs consisted of quasi-spherical graphite nanocrystals around 10 nm diameter, which were capped by amines with different hydrocarbon chains such as propylamine, octylamine, dodecylamine and octadecylamine. The introduction of nitrogen atoms and the hydrocarbon chains in the surface of the CQDs dramatically affected their photoluminescence profiles, quantum yields and solubility. The photoluminescence emission wavelength of these novel organic-soluble CQDs depended on the excitation wavelength and their quantum yields varied with the chain length of the hydrocarbon chain attached to the surface of the carbon dots.
The effect of the NH3 activation temperature of graphene/carbon composite nanofibers on their NO catalytic oxidation performance at room temperature
GUO Ze-yu, HUANG Zheng-hong, KANG Fei-yu
2017, 32(4): 338-343.
Abstract(413) PDF(496)
Abstract:
N-doped graphene/carbon composite porous nanofibers were prepared by electrospinning, followed by carbonization in nitrogen and activation in NH3 at 900, 1 000, 1 100 and 1 200℃ for 20 min, using polyacrylonitrile as a carbon precursor and graphene oxide as an additive. Their NO (50 ppm) adsorption and catalytic oxidation performances at room temperature were tested. Results showed that the catalytic oxidation activity increased with the activation temperature and a maximum conversion of 49.7% was achieved for the sample activated at 1 200℃. The adsorption capacity for NO and NO2 depended on their specific surface areas. The nitrogen-containing functional groups introduced by NH3 and the active sites formed in graphene sheets jointly increased NO conversion at room temperature.
Langmuir-Blodgett assembly of transparent graphene oxide-silver microwire hybrid films with an antibacterial property
SHI Li-fang, LIU Jun-zhe, YANG Jun-he, CAI Ling-fei, SHI Li-yun, QIU Han-xun
2017, 32(4): 344-351. doi: 10.1016/S1872-5805(17)60127-6
Abstract(450) PDF(379)
Abstract:
Silver microwires (AgMWs) were made amphiphilic by non-covalent functionalization with poly (vinyl pyrrolidone) and hexadecyl mercaptan. The Langmuir-Blodgett (LB) technique was used to transfer graphene oxide (GO) and the functionalized AgMWs (F-AgMWs)onto a quartz substrate to obtain GO-AgMW hybrid films. The films had a high optical transparency and an antibacterial property against Escherichia coli (E. coli). It is proposed that the GO layer not only acts as an adhesive layer for AgMWs, but also is acidic, which provides an ideal reaction condition for AgMWs to release the Ag+ ions that fight E. coli. The influence of pH value on the antibacterial property of the hybrid films was investigated in order to verify the proposed mechanism. Further development of this method may provide a way to produce next generation transparent multifunctional thin films with antibacterial properties.
The effect of sulfonated graphene oxide on the current-carrying wear characteristics of a resin matrix carbon brush
FENG Peng-yang, TU Chuan-jun, CHEN Zha-kun, WEI Gong, GU Zhi-ping
2017, 32(4): 352-357.
Abstract(357) PDF(350)
Abstract:
A novel resin matrix carbon brush (RMCB) was prepared by dispersing sulfonated graphene oxide (SGO) and flake graphite powder into a phenolic resin alcohol solution, followed by drying, hot rolling, pulverization, cold pressing and solidification by heat treatment. The current-carrying wear performance of the RMCB was tested by using it in a heavy-duty industrial motor at different on-load voltages from 200 to 240 V for 4 h and examining it after use. The microstructure was characterized by XRD, SEM, EDS and TEM. Results show that the flake graphite particles were bridged by SGO and the ground surface of the brush exhibited an interconnected carbon structure. The wear rate of the RMCB with SGO was 2.06×10-7 mg·N-1·m-1 at 220 V, which was 31.3% of that of the RMCB without SGO. The combined action of arc erosion wear, oxidative wear and adhesive wear was the dominant wear mechanism of the brush with and without SGO during the current-carrying wear test.
Adsorption and desorption behavior of benzene and toluene on porous carbon monoliths
WANG Mei, JIA Xian-feng, MA Cheng, WANG Ji-tong, SONG Zhen-chao, LONG Dong-hui, QIAO Wen-ming, LING Li-cheng
2017, 32(4): 358-364.
Abstract(398) PDF(429)
Abstract:
Highly porous carbon monoliths with good mechanical strength were prepared by the sol-gel polymerization of phenolic resin in oxidized polyacrylonitrile fiber felts, ambient drying, carbonization at 800℃ for 2 h and CO2 activation at 950℃ for 1 to 3 h. Their microstructure and pore structure were investigated by SEM, TEM and N2 adsorption. Their adsorption/desorption performance for benzene and toluene was measured by the gravimetric method. It is found that the carbon monoliths have a typical fiber-reinforced aerogel structure and the sample activated for 3 h (ACM-3) has a well-developed microporous structure with a BET surface area of 1 872 m2/g and pore volume of 0.97 cm3/g. ACM-3 shows high adsorption capacities of 117 and 287 mg/g for 50 ppm benzene and toluene, respectively, and the fastest adsorption/desorption kinetics. The Langmuir, Freundlich and DR isotherm models are used to fit the experimental adsorption data and the DR model shows the highest correlation coefficient. Moreover, ACM-3 has an excellent cyclic stability. The as-prepared carbon monoliths are promising adsorbents for the adsorption of volatile organic compounds in indoor air purification.
Ablation performance of a 4D-braided C/C composite in a parameter-variable channel of a Laval nozzle in a solid rocket motor
HUI Wei-hua, BAO Fu-ting, WEI Xiang-geng, LIU Yang
2017, 32(4): 365-373. doi: 10.1016/S1872-5805(17)60128-8
Abstract(614) PDF(410)
Abstract:
Ablation of a 4D-braided C/C composite fabricated with axial rods in the parameter-variable channel of a Laval nozzle (or a convergent-divergent nozzle, a tube that is pinched in the middle) was performed in the experimental conditions of a solid rocket motor. Gas-solid flow and erosion were also simulated with the discrete phase model. The ablation of the composite was caused by thermochemical and mechanical erosion and was analyzed based on the morphology of different sections of the channel in the nozzle with different angles between the gas flow direction and the surface of the composite (ablation angle). Results showed that the ablation behavior was related to the velocity, concentration, collision angle to the surface and the wall shear force of particles in the ablation gas. The ablation gradually increased with the rate of gas flow and was a maximum at the maximum ablation angle of 45° in the compression section. In the expansion section, beyond the throat, ablation decreased significantly. The maximum linear and mass ablation rates were 0.056 mm/s and 0.157 kg/m2·s, respectively. The carbon fibers formed a tapered tip, whose sharpness depended on the ablation angle and the braiding direction.
A CNT/TiO2-x Nx composite as a high electrocatalytic active counter electrode for a dye-sensitized solar cell
YU Chang, CUI Dan, LIU Cheng-jing, MENG Xiang-tong, LIU Zhi-qiang, QIU Jie-shan
2017, 32(4): 374-379.
Abstract(385) PDF(418)
Abstract:
A CNT/TiO2-x Nx composite was synthesized by an integrated hydrothermal and NH3 annealing method. The as-synthesized composite was characterized by XRD, SEM, TEM and XPS, and its catalytic activity as a counter electrode for a dye-sensitized solar cell (DSSC) was investigated by cyclic voltammetry, Tafel-polarization, electrochemical impedance spectroscopy and I-V techniques. Results show that nitrogen was successfully doped into the TiO2 crystal lattice. CNTs with a diameter of 30-50 nm interconnect with the TiO2-x Nx nanowires with a diameter of 3-8 nm, leading to a network structure. Benefiting from the high electrocatalytic activity of TiO2-x Nx and the high conductivity of CNTs, the composite demonstrates a higher power conversion efficiency (7.16%) than pure CNTs (4.67%) as the counter electrode of the DSSC, and this value is comparable to that of a noble Pt electrode.
Synthesis of nitrogen-doped graphitic carbon nanocapsules from a poly(ionic liquid) for CO2 capture
LIU Lei, LU Juan, ZHANG Yi-xin, LIU Meng, YU Yi-feng, CHEN Ai-bing
2017, 32(4): 380-384. doi: 10.1016/S1872-5805(17)60129-X
Abstract(340) PDF(403)
Abstract:
A poly(ionic liquid) was prepared from an ionic liquid monomer that was obtained by the reaction of 1-vinylimidazole, 4-vinyl-benzene chloride with 2,6-di-tert-butyl-4-methylphenol. The poly(ionic liquid) was mixed with K3[Fe(CN)6] and a 5 nm silica colloidal sol, carbonized at 900℃ for 4 h, and sequentially treated with HNO3 and NaOH to remove the iron and silica to obtain nitrogen-doped graphitic carbon nanocapsules. The iron and silica acted as a graphitization catalyst and template, respectively. The nitrogen-doped graphitic carbon nanocapsules have a diameter of 50 nm and a wall thickness of 6 nm and have a high adsorption capacity and good recyclability for CO2 capture. The addition of SiO2 nanoparticles in the synthesis significantly increased the specific surface area from 100.4 to 865.7 m2·g-1 and the CO2 adsorption capacity from 0.76 to 2.14 mmol·g-1.