Ultrathin transition metal carbides are a class of emerging 2-D materials with many intriguing properties and applications. Here, we report the transport measurements on high-quality ultrathin MoC crystals, which are synthesized by a chemical vapor deposition method. We demonstrate 2-D nature of the observed superconductivity in ultrathin MoC crystals, being consistent with a Berezinskii-Kosterlitz-Thouless transition. As the sample thickness decreases, the MoC crystals exhibit negative magnetoresistance behavior at low magnetic fields deep in the superconducting state. We attribute these results to strong phase fluctuations of the superconducting order parameters near the superconductor-insulator transition. Our results demonstrate that these high-quality ultrathin MoC crystals provide an appealing platform to gain insights into 2-D superconductivity in a clean system.

Song Shuang    Wang    Xu Chuan    成会明     任文才    Ning Kang   

IEEE Transactions on Magnetics

2017

Ji Liang    Li Feng    成会明     Béguin François   

Energy Storage Materials

2017

Flexible electrochemical energy storage (FEES) devices have received great attention as a promising power source for the emerging field of flexible and wearable electronic devices. Carbon nanotubes (CNTs) and graphene have many excellent properties that make them ideally suited for use in FEES devices. A brief definition of FEES devices is provided, followed by a detailed overview of various structural models for achieving different FEES devices. The latest research developments on the use of CNTs and graphene in FEES devices are summarized. Finally, future prospects and important research directions in the areas of CNT- and graphene-based flexible electrode synthesis and device integration are discussed.

Wen Lei    Feng Li    成会明    

Advanced Materials

2016

Liang Ji    Li Feng    成会明    

Energy Storage Materials

2016

Lithium-sulfur (Li-S) battery is one of the most promising candidates for the next generation energy storage solutions, with high energy density and low cost. However, the development and application of this battery have been hindered by the intrinsic lack of suitable electrode materials, both for the cathode and anode. Recently, tremendous progress has been achieved in improving the battery performance by modifying the electrodes by the incorporation of various functional carbon materials. Carbons used in Li-S batteries not only act as conductive additives, but also as shuttling preventers, spatial confiners and anode protectors, etc. In this review, we highlight the evolution of the functionality of carbon materials with the development of Li-S batteries. The scientific understandings of the fundamental design of the materials' structure and chemistry in relation to the battery performance are summarized. A way to design next generation Li-S batteries can be drawn through this review.

Liang Ji    Sun Zhen-Hua    Feng Li    成会明    

Energy Storage Materials

2016

The structural evolution of electrochemically prelithiated FeO nanoparticles confined in carbon nanotubes (CNTs) during lithium insertion/extraction is studied by in situ transmission electron microscopy. It is found that the aggregation and coarsening of Fe core-containing LiO (Fe@LiO) nanograins formed during the charge process are prevented by the spatial restriction of the CNTs. A high reversible capacity of 2071 mA h g for the encapsulated FeO nanoparticles in CNTs is demonstrated when the material is used as the anode of lithium ion batteries. This is the highest reversible capacity ever reported for an FeO electrode. The significantly improved lithium storage capacity of the FeO nanoparticles is attributed to the extra lithium storage due to the enhanced interfacial lithium storage and reversible reaction of LiOH to form LiH and solid-electrolyte-interphase conversion originating from the nanoconfinement of CNTs as well as the very small particle size of the Fe@LiO nanograins and their good electrical contact with CNTs.

Wanjing Yu    Lili li Zhang    Pengxiang Hou    Li Feng    Chang Liu    成会明    

Advanced Energy Materials

2016

Liang Ji    Li Feng    成会明    

Energy Storage Materials

2016

With an aim to enhance the photocatalytic activity, Pt loaded TiO-Al-MCM-41 catalysts with high surface area were synthesized by a multistep route. The waste of the rice processing, rice husk (RH), was used as the precursor for the extraction of silica. The diffuse reflectance and photoluminescence spectroscopy revealed the extension of the absorption edge in the visible region and exciton trapping nature of the dispersed platinum. The structural analysis was carried out by XRD, whereas X-ray photoelectron spectroscopy identified the chemical states of the components of the synthesized powders. The BET surface area measurements revealed the reduction in the surface area and pore volume with the increasing platinum loading. TEM micrographs showed the uniform distribution of TiO and Pt nanoparticles at the surface of Al-MCM-41. The photocatalytic efficiency of the synthesized powders as photocatalysts was obtained for the removal of 100ppm CN from aqueous solution in fluorescent blue light exposure. Compared to unsupported TiO, the Pt-loaded catalysts exhibited substantially high activity for the removal of CN. A plausible mechanism for the removal of cyanide ions was proposed. The catalysts showed excellent stability and reproducibility in the successive use.

Mohammad Kadi    Abdul Hameed    Mohamed    Iqbal mohammad ibrahim Ismail    Alangari Yaser    成会明    

Arabian Journal of Chemistry

2016

Zhang Feng    Hou Peng-Xiang    Chang Liu    Wang Bing-Wei    Jiang Hua    Chen Mao-Lin    Sun Dong-ming    Li Jin-Cheng    Cong Hong-Tao    Esko Kauppinen    成会明    

Nature Communications

2016

Ultrathin transition metal carbides are a class of developing two-dimensional (2D) materials with superconductivity and show great potentials for electrical energy storage and other applications. Here, we report low-temperature magnetotransport measurements on high-quality ultrathin 2D superconducting α-MoC crystals synthesized by a chemical vapor deposition method. The magnetoresistance curves exhibit reproducible oscillations at low magnetic fields for temperature far below the superconducting transition temperature of the crystals. We interpret the oscillatory magnetoresistance as a consequence of screening currents circling around the boundary of triangle-shaped terraces found on the surface of ultrathin MoC crystals. As the sample thickness decreases, the MoC crystals exhibit negative magnetoresistance deep in the superconducting transition regime, which reveals strong phase fluctuations of the superconducting order parameters associated with the superconductor-insulator transition. Our results demonstrate that the ultrathin superconducting MoC crystals provide an interesting system for studying rich transport phenomena in a 2D crystalline superconductor with enhanced quantum fluctuations.

Wang    Xu Chuan    Zhibo Liu    Chen Long    Xiuliang Ma    成会明     任文才    Ning Kang   

ACS Nano

2016