Motivated by the ion migration mechanism proposed by David et al. [J. Am. Chem. Soc. 129 (2007) 1594-1601], we mechanically mill the Li₃N/Co powder mixture to obtain defective Li₃N-type structure with enhanced Li⁺ mobility. Compared with Li₃N, the hydrogen storage property of such defective phase is markedly improved, presumably due to the ion-migration-enhancing effect from the incorporation of Co and Fe (from milling utensils). During subsequent cycling, however, this effect cannot persist due to the precipitation of Co-Fe alloy upon hydrogenation. The close correlation between Co-Fe incorporation/precipitation and property variation of Li₃N hydrogen storage material provides a preliminary evidence to support the ion migration mechanism.

Lai Peng Ma;Ping Wang;Hong Bin Dai;Ling Yan Kong;会明 成

Journal of Alloys and Compounds

2008-10-20

This work reports a facile hydrothermal approach to directly grow anatase TiO₂ crystals with exposed {001} facets on titanium foil substrate by controlling pH of HF solution. The mechanistic role of HF for control growth of the crystal facet of anatase TiO₂ crystals has been investigated. The results demonstrate that controlling solution pH controls the extent of surface fluorination of anatase TiO₂, hence the size, shape, morphology, and {001} faceted surface area of TiO₂ crystals. The theoretical calculations reveal that {001} faceted surface fluorination of anatase TiO₂ can merely occur via dissociative adsorption of HF molecules under acidic conditions while the adsorption of Na⁺F ^- is thermodynamically prohibited. This confirms that the presence of molecular form of HF but not F^- is essential for preservation of exposed {001} facets of anatase TiO₂. Anatase TiO₂ crystals with exposed {001} facets can be directly fabricated on titanium foil by controlling the solution pH 5.8. When pH is increased to near neutral and beyond (e.g., pH ≥ 6.6), the insufficient concentration of HF ([HF] 0.04%) dramatically reduces the extent of surface fluorination, leading to the formation of anatase TiO₂ crystals with {101} facets and titanate nanorods/nanosheets. The anatase TiO₂ nanocrystals with exposed {001} facets exhibits a superior photoelectrocatalytic activity toward water oxidation. The findings of this work clarify the mechanistic role of HF for controlling the crystal facet growth, providing a facile means for massive production of desired nanostructures with high reactive facets on solid substrates for other metal oxides.

Haimin Zhang;Yun Wang;Porun Liu;Yanhe Han;Xiangdong Yao;Jin Zou;会明 成;Huijun Zhao

ACS applied materials & interfaces

2011-7-27

Preparation of dense carbon materials without use of any binder was attempted, effect of grinding treatment on the characteristics of raw petroleum needle coke and on the properties of the sintered carbon compacts was investigated, and the sintering mechanizm of the coke after grinding was discussed. It was found that the coke particle size and crystalline size was decreased and the specific surface area of the coke was increased with grinding, and the influence was obvious up to 20 hours grinding treatment. The interlayer spacing of the coke after graphitization at 2773 K was gradually increased and the a-axis constant was marginally reduced with the grinding time. Results from the sintering experiment show that carbon materials can be sintered from the ground coke, and the density and flexural strength of the sintering compacts reached stable values of 1.8 g cm^-3 and about 70 MPa, respectively, after 20 hours grinding of the coke. The sintering ability of the coke after grinding was considered to result from the increase of surface energy, lattice distortion energy and fraction of volatile matters of the coke, which were induced by grinding treatment.

会明 成;M. Liu;Z. H. Shen;J. Z. Xi;H. Sano;Y. Uchiyama;K. Kobayashi

Carbon

1997

Energy is one of the most important issues in this century. With the rapid depletion of fossil fuel and increasingly worsened environmental pollution caused by vast fossil energy consumption, it is in a high demand to make efficient use of the present energy sources and to seek for renewable and clean energy sources. Therefore, research and development of new energy storage materials and devices are receiving worldwide concern and increasing research interest.

会明 成

2010

The reactivity of a photocatalyst is basically influenced by its surface atomic and linked electronic structure. Tuning different crystal facets is becoming an important strategy to optimize the reactivity of a photocatalyst for targeted reactions. Here we report a facile and new route of synthesizing a quasi-cubic-like WO ₃ crystal with a nearly equal percentage of {002}, {200} and {020} facets, and a rectangular sheet-like WO ₃ crystal with predominant {002} facet by controlling acidic hydrolysis of crystalline WB. As a result of electronic structure effects induced by crystal facet, the quasi-cubic-like WO ₃ crystal with a deeper valence band maximum shows a much higher O ₂ evolution rate in photocatalytic water oxidation than the rectangular sheet-like WO ₃ crystal. The latter, with an elevated conduction band minimum of 0.3 eV, is able to photoreduce CO ₂ to generate CH ₄ in the presence of H ₂O vapor.

Ying Peng Xie;Gang Liu;Lichang Yin;会明 成

Journal of Materials Chemistry

2012-4-14

Advanced electrochemical energy storage devices (EESDs) that can store electrical energy efficiently while being miniature/flexible/wearable/load-bearing are much needed for various applications ranging from flexible/wearable/portable electronics to lightweight electric vehicles/aerospace equipment. Carbon-based fibers hold great promise in the development of these advanced EESDs (e.g., supercapacitors and batteries) due to their being lightweight, high electrical conductivity, excellent mechanical strength, flexibility, and tunable electrochemical performance. This review summarizes the fabrication techniques of carbon-based fibers, especially carbon nanofibers, carbon-nanotube-based fibers, and graphene-based fibers, and various strategies for improving their mechanical, electrical, and electrochemical performance. The design, assembly, and potential applications of advanced EESDs from these carbon-based fibers are highlighted. Finally, the challenges and future opportunities of carbon-based fibers for advanced EESDs are discussed.

Shaohua Chen;Ling Qiu;会明 成

Chemical Reviews

2020-3-11

In this work, a new technique-photothermal-resistance technique, is developed to characterize the thermophysical properties of one-dimensional micro/nanostructures. In this technique, the to-be-measured thin wire/tube is suspended over two electrodes and is irradiated with a periodically modulated laser beam. The laser beam induces a periodical temperature variation in the wire/tube, which will result in a periodical change of its electrical resistance. A DC current is applied to the sample, and the resulting periodical voltage variation over the wire is measured and used to extract the thermophysical properties of the wire/tube. A 25.4-μm thick platinum wire is used as the reference sample to verify this new technique. Sound agreement is obtained between the measured thermal conductivity and the reference value. Applying the photothermal-resistance technique, the thermal diffusivity of single-wall carbon nanotube bundles is measured. The measured thermal diffusivity for three different single-wall carbon nanotube bundles is 2.98×10^-5 m²/s, 4.41×10^-5 m ²s and 6.64×10^-5 m²/s, respectively. These values are much less than the thermal diffusivity of graphite.

Jinbo Hou;Xinwei Wang;Chang Liu;会明 成

2006

The current development trend towards miniaturized portable electronic devices has significantly increased the demand for ultrathin, flexible and sustainable on-chip micro-supercapacitors that have enormous potential to complement, or even to replace, micro-batteries and electrolytic capacitors. In this regard, graphene-based micro-supercapacitors with a planar geometry are promising micro-electrochemical energy-storage devices that can take full advantage of planar configuration and unique features of graphene. This review summarizes the latest advances in on-chip graphene-based planar interdigital micro-supercapacitors, from the history of their development, representative graphene-based materials (graphene sheets, graphene quantum dots and graphene hybrids) for their manufacture, typical microfabrication strategies (photolithography techniques, electrochemical methods, laser writing, etc.), electrolyte (aqueous, organic, ionic and gel), to device configuration (symmetric and asymmetric). Finally, the perspectives and possible development directions of future graphene-based micro-supercapacitors are briefly discussed.

Zhong Shuai Wu;Xinliang Feng;会明 成

National Science Review

2014

In order to achieve the goals of thermal protection, structure load-bearing and weight reduction of thermal protection materials, a multifunctional integrated composite is fabricated by the combination of slurry infiltration and isothermal chemical vapor infiltration, which has a porous C_f/C-ZrB₂-SiC core between two outer layers of compact C_f/C-ZrB₂-SiC and C_f/C-SiC. Compared to a C_f/SiC composite with a density of 2.1gcm^-3, the material presents a low density of 1.65gcm^-3 and a 65% lower thermal conductivity in-thickness (3.29Wm^-1K^-1), while its flexural strength is 260MPa, only 16% lower. In addition, the integrated composite exhibits a good ablation resistance with a linear ablation rate of 0.79μm/s for 1000s.

Chenglong Hu;Shengyang Pang;Sufang Tang;Yongcai Wang;会明 成

Journal of the European Ceramic Society

2015

A Fe-N impregnated carbon in a hybrid with in-situ grown graphene from hierarchical porous carbon has been obtained for high-performance oxygen reduction reaction (ORR) catalysis. This hybrid material combines the desirable characteristics for the ORR, including Fe-N active sites, high surface area, good electron conductivity, and hierarchical channels for mass diffusion. As a result, this catalyst exhibits a very positive reaction onset potential (−0.05 V vs. Ag/AgCl), a high ORR current density, and a complete four-electron ORR pathway, which are even better than a commercial 20% Pt/C catalyst. We further reveal the synergistic ORR enhancement from the controlled Fe-N impregnation in the doped carbon-graphene hybrid.

Sihui Wang;Xiao Yan;Kuang Hsu Wu;Xuemin Chen;Jian Min Feng;Pengyi Lu;会明 成;Ji Liang;Shi Xue Dou

Carbon

2019-4