Chong Xie

In Situ Synthesis of Carbon Nanotube Hybrids with Alternate MoC and MoS2 to Enhance the Electrochemical Activities of MoS2

Molybdenum disulfides and carbides are effective catalysts for hydrogenation and hydridesulfurization, where MoS2 nanostructures are also highly promising materials for lithium ion batteries. High surface-to-volume ratio and strong interactions with conducting networks are crucial factors for their activities. A new hybrid structure of multiwalled carbon nanotube (MWCNT) with alternate MoC nanoparticles and MoS2 nanosheets (MoS2 + MoC-MWCNT) has been synthesized by controlled carburization of core-shell MoS2-MWCNT hybrid nanotubes and demonstrated by HRTEM, FFT, XRD, and Raman scattering. The MoS2 nanosheets (∼10 nm) remain tightly connected to MWCNT surfaces with {001} planes in parallel to MWCNT walls and the highly crystallized α-MoC particles (∼10 nm) are adhered to MWCNTs at angles of 60-80° between {111} planes and MWCNT walls. The electrochemical performances of the hybrid structures have been demonstrated as anodes for lithium ion batteries to be significantly increased by breaking MoS2 nanotubes into nanosheets (patches) on MWCNT surfaces, especially at high current rates. The specific capacities of MoS2 + MoC-MWCNT sample with ∼23% MoS2 have been demonstrated to be higher than those of MoS2-MWCNTs containing ∼70% MoS2.

Carbon-doped titania nanoplates with exposed {001} facets: facile synthesis, characterization and visible-light photocatalytic performance

C-doped TiO2 nanoplates (CTNP) with exposed {001} facets were successfully synthesized by hydrothermal treatment of TiC powder in a HF–HNO3 mixed aqueous solution for the first time. The effects of hydrothermal temperature (140, 160, 180 and 200 °C) on the crystal phase, morphology, specific surface area and porous properties, surface element composition, optical response properties of the resultant samples were investigated in detail, and the photocatalytic activities of these obtained CTNP samples for the degradation of methylene blue (MB) were evaluated under visible light irradiation. The results showed that precursor cubic TiC was transformed into anatase TiO2 with the morphology of well-defined nanoplate completely after hydrothermal treatment for 30 h. The specific surface area of CTNP was significantly improved in comparison with that of micrometer sized C-doped TiO2 plates (CTP) due to smaller particle size. Due to C-doping, CTNP presented red-shift absorption edge, which supported it with strong visible-light response. All these factors led to as-prepared CTNP having more excellent visible-light photocatalytic activity in comparison with micrometer sized CTP. The CTNP synthesized at 180 °C presented the optimal visible-light photocatalytic activity with a high reaction rate constant (0.03692 min−1) among the four CTNP samples. Based on the results of the present study, a reasonable mechanism of photocatalysis on CTNP under visible light was proposed.

Binding SnO2 nanoparticles onto carbon nanotubes with assistance of amorphous MoO3 towards enhanced lithium storage performance

We report the synthesis of a novel SnO2/MoO3/carbon nanotubes (CNTs) hybrid (denote as SMC) via hydrothermally treating aqueous SnCl4-Na2MoO4-CNTs suspension. The hydrolysis of SnCl4 promotes the precipitation of Na2MoO4, resulting in the simultaneous coprecipitation of the amorphous MoO3 and SnO2 nanoparticles which attach onto the CNTs (Note that no MoOx is produced in the absence of SnCl4). When used as anode materials for lithium ion batteries (LIBs), the as-prepared SMC hybrid delivers a high reversible capacities of 1032 and 887mAh/g after 50 cycles at current densities of 200 and 500mA/g, respectively, and still retains a reversible capacity of 496mAh/g even after 200 cycles at a higher rate of 2A/g, which shows much better lithium storage performance than that of the counterpart hybrid of SnO2/CNTs (denote as SC, with only 569mAh/g after 50 cycles at 200mA/g). The enhanced electrochemical performance of SMC can be attributed to a synergistic effect, namely, MoO3 not only confines SnO2 nanoparticles onto the CNTs but also brings additional lithium storage capacity, while the flexible conductive CNT networks facilitate the charge transfer and electrolyte diffusion.