Herein, SiO2 nanotubes have been fabricated via a facile two step hard-template growth method and evaluated as an anode for Li-ion batteries. SiO2 nanotubes exhibit a highly stable reversible capacity of 1266 mAhg−1 after 100 cycles with negligible capacity fading. SiO2 NT anodes experience a capacity increase throughout the first 80 cycles through Si phase growth via SiO2 reduction. The hollow morphology of the SiO2 nanotubes accommodates the large volume expansion experienced by Si-based anodes during lithiation and promotes preservation of the solid electrolyte interphase layer. The thin walls of the SiO2 nanotubes allow for effective reduction in Li-ion diffusion path distance and, thus, afford a favorable rate cyclability. The high aspect ratio character of these nanotubes allow for a relatively scalable fabrication method of nanoscale SiO2-based anodes.
Synthesis of atomically thin MoS2 layers and its derivatives with large‐area uniformity is an essential step to exploit the advanced properties of MoS2 for their possible applications in electronic and optoelectronic devices. In this work, a facile method is reported for the continuous synthesis of atomically thin MoS2 layers at wafer scale through thermolysis of a spin coated‐ammonium tetrathiomolybdate film. The thickness and surface morphology of the sheets are characterized by atomic force microscopy. The optical properties are studied by UV–Visible absorption, Raman and photoluminescence spectroscopies. The compositional analysis of the layers is done by X‐ray photoemission spectroscopy. The atomic structure and morphology of the grains in the polycrystalline MoS2 atomic layers are examined by high‐angle annular dark‐field scanning transmission electron microscopy. The electron mobilities of the sheets are evaluated using back‐gate field‐effect transistor configuration. The results indicate that this facile method is a promising approach to synthesize MoS2 thin films at the wafer scale and can also be applied to synthesis of WS2 and hybrid MoS2‐WS2 thin layers.
Oxygen annealing of thick MoS2 films results in randomly oriented and controllable triangular etched shapes, forming pits with uniform etching angles. These etching morphologies differ across the sample based on the defect sites situated on the basal plane surface, forming numerous features in different bulk sample thicknesses.
In this work, we report the synthesis of an three-dimensional (3D) cone-shape CNT clusters (CCC) via chemical vapor deposition (CVD) with subsequent inductively coupled plasma (ICP) treatment. An innovative silicon decorated cone-shape CNT clusters (SCCC) is prepared by simply depositing amorphous silicon onto CCC via magnetron sputtering. The seamless connection between silicon decorated CNT cones and graphene facilitates the charge transfer in the system and suggests a binder-free technique of preparing lithium ion battery (LIB) anodes. Lithium ion batteries based on this novel 3D SCCC architecture demonstrates high reversible capacity of 1954 mAh g(-1) and excellent cycling stability (>1200 mAh g(-1) capacity with ≈ 100% coulombic efficiency after 230 cycles).
Using chemical vapor deposition technique, a novel 3D carbon nano-architecture called a pillared graphene nanostructure (PGN) is in situ synthesized. The fabricated novel carbon nanostructure consists of CNT pillars of variable length grown vertically from large-area graphene planes. The formation of CNTs and graphene occurs simultaneously in one CVD growth treatment. The detailed characterization of synthesized pillared graphene shows the cohesive structure and seamless contact between graphene and CNTs in the hybrid structure. The synthesized graphene-CNT hybrid has a tunable architecture and attractive material properties, as it is solely built from sp2 hybridized carbon atoms in form of graphene and CNT. Our methodology provides a pathway for fabricating novel 3D nanostructures which are envisioned for applications in hydrogen storage, nanoelectronics, and supercapacitors.
Sustainable energy is currently limited by the ability of materials to store energy and deliver it on demand. Allotropes of carbon are attractive for their potential for use in energy storage due to low weight, high chemical stability and low production cost. Carbon nanotubes and graphene can be combined to provide an effective three-dimensional material with high conductivity and high surface area. We demonstrate the use of block copolymers to obtain patterned arrays of iron nanoparticles which give rise to ordered carbon nanotubes with good size distribution. A one-step chemical vapor deposition process for large-area fabrication of the graphene and carbon nanotube hybrid structure is described. Following chemical vapor deposition the hybrid material is demonstrated in a supercapacitor device. The fabricated supercapacitor exhibits high electrical conductivity, and has potential for extremely high energy storage capability.
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