A newly developed, focused-jet, vertical style electrospinning process was employed to synthesize nanofibers of TiO2 doped with 2% and 2.5% w/v Ag nanoparticles. The as-spun nanofibers were calcined at 510 °C for 24 h in a tube furnace, with a ramp-rate of 5 °C/min, to yield polycrystalline nanofibers. Structural characterization of the prepared nanofibers was done using HR-TEM operated at 200 kV. High-resolution lattice-fringe measurements showed the presence of a mixed-phase anatase and rutile TiO2 nanostructure along with elemental Ag nanoparticles. BET analysis showed an average specific surface-area of 18.31 m2/g for the catalyst nanofibers. To measure the photocatalytic activity, a model compound, rhodamine-B dye, was used. Experimental results showed decay rates of 10.64 x 10-3 min-1 and 12.32 x 10-3 min-1 for the decay of rhodamine-B dye by TiO2/2% Ag and TiO2/2.5% Ag nanoparticles respectively.

Conventional carbon electrode supports for platinum used in proton exchange membrane (PEM) fuel cell assemblies have issues related to carbon corrosion at typical cell operating and transient conditions. This corrosion gives rise to the evolution of greenhouse gases such as CO2, eventually degrading the carbon support and causing a loss of the catalyst specific area necessary to achieve the desired electrochemical performance. In this study, preliminary results are presented for Pt-functionalized TiO2 nanotube arrays as cathode catalyst supports for PEM fuel cells. The electrochemically synthesized TiO2 nanotube arrays were functionalized by different weight % of Pt via a solution-based approach using a dilute aqueous salt solution of hexachloroplatanic acid. Electron-beam based characterization techniques were used to study the structural and morphological features of the as-synthesized TiO2 nanotube arrays and functionalized Pt/TiO2 nanotube arrays. The electrochemical performance of the functionalized TiO2 nanotube arrays was studied by using cyclic voltammetry.

Nanoarchitectures consisting of single crystalline Co3O4 spheres and multi-walled carbon nanotubes (MWCNTs) have been constructed successfully. The effect of reaction temperature on the morphology of the products reveal that the growth rate dictates the shape and size of Co3O4 beads on and around MWCNTs. Single crystalline Co3O4 spheres around MWCNTs can be produced in large scale by elevating reaction temperature for the increased growth rate. The electrochemical properties of the hybrid materials were investigated by cyclic voltammetry (CV) and galvanostatic charge/discharge tests. The supercapacitors made with the nanoarchitectures show high specific capacitance of 445 F/g at a current density of 0.1 A/g and exhibit excellent cycling stability.

We performed pulsed laser ablation of titanium dioxide (TiO2) target in O2 background gas. Effects of background gas pressure and substrate target distance on the structure of deposited films are clarified. The hierarchical structures are observed when we change scale of observation. The film deposited on the substrate is composed of primary nanocrystal and secondary porous-aggregated-nanostructures. The primary nanocrystal changes from anatase to rutile phase with increasing background gas pressure or substrate target distance. The porosity of secondary aggregated structure increases with increasing background gas pressure or substrate target distance. The similarity between the effects of background gas and substrate target distance indicates that confinement of the plume between target and substrate is important for structural formation. The non-equilibrium aggregation processes of nanocrystals in the plume and on the substrate are essential for the hierarchical structure of the nanocrystal film.

Microporous-macroporous carbononaceous monolith-type materials, prepared through a hard template method using silica as exo-templating matrices, have been impregnated by an etheric solution of LiBH4 to prepare LiBH4@Carbon samples. It has been shown that the amorphous character of LiBH4 is largely favoured when developing the carbon microporosity (pores smaller than 2 nm) and that LiBH4 dehydrogenation is strongly enhanced at low temperatures. The onset temperature of dehydrogenation can be decreased to 200°C and hydrogen capacity reaching 4.0 wt.% is obtained at 300°C with the carbon having the largest microporous volume, whereas the hydrogen release for bulk LiBH4 is negligible at the same temperature. In addition to some irreversible reactions with carbon surface groups the explanation for such modification could lie in the LiBH4 destabilization through confinement to the nanoscale range and associated amorphization.

The synthesis of hierarchically assembled Al-doped ZnO layers by Pulsed Laser Deposition (PLD) at room temperature was investigated. PLD was performed in a background pressure of 100 Pa O2 to deposit clusters in a low energy regime and obtain nano- and mesostructures resulting from a hierarchical assembly of nanoclusters. We here analyzed the effects of varying the gas flow rate on mesoscale morphology, mass density and optical properties. The variation of the target-to-substrate distance was also investigated, identifying its effects on mass density and film morphology. The optimization of optical properties in terms of transparency and light scattering capability is of potential interest for photovoltaic applications.

In the present study, poly (3, 4-ethylenedioxythiophene) (PEDOT) nanostructures were obtained by oxidative polymerization of monomer ‘3, 4-ethylenedioxythiophene’ in the presence of poly (acrylic acid) (PAA) in FeCl3 as an oxidizing agent. The PEDOT nanostructures were characterized using the Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) techniques respectively. The morphology of PEDOT nanostructures revealed flowerlike-shape agglomerates with an increase in the concentrations of PAA. The SEM, TEM and FTIR studies revealed that the presence of PAA could only induce a change in morphology during polymerization, but could not influence the molecular structure of the PEDOT nanostructures. The synthesized PEDOT nanostructures were used as electrode material for supercapacitor. The electrochemical capacitive properties of the PEDOT nanostructures were investigated with the Cyclic Voltammetry (CV), galvanostatic charge–discharge and electrochemical impedance spectroscopy (EIS) techniques in the three-electrode cell system. The capacitance of the PEDOT electrode was measured in 0.1M LiClO4 and 2M H2SO4 electrolytes. The highest specific capacitance value of 215F/g for a PEDOT nanostructured electrode was calculated in 1 M H2SO4 electrolyte.

There are several significant challenges that must be overcome for PEM fuel cell commercialization such as electrode flooding, carbon corrosion, and significant cost due to the high loading of the platinum catalyst. Thus, a new structure is proposed for the cathode catalyst support consisting of Si/TiOx core/shell nanowires with branched structures, which has the potential to reduce electrode flooding, increase stability, and dramatically reduce the required Pt loading. In this study, Pt-coated Si/TiOx core/shell nanowires with and without branches are compared. The Pt surface area on supports with branch structures was calculated to be more than 4 times larger than on supports without branch structures, while keeping the Pt loading at only about 0.1 mg/cm2 (for the samples with branched structures). SEM, XRD, AES, and TEM were used to characterize the morphologies and structures of the as-prepared samples. Branched Si/TiOx core/shell nanowire structures may be a promising catalyst support to enable commercialization of highly cost-efficient PEM fuel cells and to promote an era of clean energy usage.

Eu3+/Tb3+co-doped YBO3 three-dimensional (3D) microstructures have been hydrothermally prepared by adjusting solvent and the molar ratio of Y3+ to B (Y/B) at 180 °C. The whole process was carried out under alkaline conditions without the use of any surfactant or catalyst. Characterizations of the samples are carried out using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution TEM (HRTEM). The photoluminescence (PL) colors of YBO3 sample co-doped with Eu3+ and Tb3+ under ultraviolet excitation can be tuned from red, through yellow and green-yellow, to green by changing the relative doping concentrations of the two activator ions. These phosphors with multicolor emissions in the visible region be potentially used as labels for light-display systems, optoelectronic devices and biological molecules.

A fundamental challenge in solar-thermal-electrical energy conversion is the thermal stability of materials and devices at high operational temperatures. This study focuses on the thermal stability of selective emitters for solar thermophotovoltaic (STPV) systems to enhance the conversion efficiency. 2-D photonic crystals are periodic micro/nano-scale structures that are designed to affect the motion of photons at certain wavelengths. The structured patterns, however, lose their structural integrity at high temperature, which disrupts the tight tolerances required for spectral control of the thermal emitters. Through analytical studies and experimental observations, the four major mechanisms of thermal degradation of 2-D photonic crystal are identified: oxidation, grain growth and re-crystallization, surface diffusion, and evaporation and re-condensation. In this work, the design of a flat surface photonic crystal (FSPC) is proposed and experimental validations are performed.

Polyaniline nanofibers (PANI-NFs)/graphite oxide (GO) nanocomposites with excellent interfacial interaction and elongated fiber structures were synthesized via a facile interfacial polymerization method. This method efficiently exfoliated the expanded layer structure of GO into individual sheet and thus significantly enhanced the specific surface area. The reduced diameter of PANI-NFs in PANI-NF/GO than that of pure PANI-NFs could shorten the diffusion distance and enhance the electro-active sites. The PANI-NFs/GO hybrid materials showed orders of magnitude enhancement in capacitance and better cycling stability than that of individual GO and PANI-NF components.

A novel flat, wood-based carbon material with heterogeneous pores, referred to as flat lignocellulosic carbon material (FLCM), was successfully fabricated by carbonizing samples of the softwood Picea jezoensis (Ezomatsu or Jezo spruce, a Japanese conifer). Simultaneous improvements of the specific surface area of the FLCM and the affinity of electric double-layer capacitor (EDLC) for electrolyte solvents were achieved by vacuum ultraviolet/ozone (VUV/O3) treatment. The specific surface area of the VUV/O3-treated FLCM showed a 50% increase over that of the original FLCM. The spectra measured by X-ray photoelectron spectroscopy (XPS) indicated that the number of O-C=O (carboxyl or ester) bonds increased, whereas the number of C-C bonds decreased. Additionally, the feasibility of using the FLCM as a self-supporting electrode in EDLCs was examined by measuring the electrochemical properties in a three-electrode system. The FLCM was confirmed as an appropriate self-supporting EDLC electrode material without warps and cracks. In addition, the FLCM can be used without any binder. Realization of FLCM-based EDLC electrodes with bendability, an area of several tens of square centimeters, and no risk of warp or crack formation, were indicated. Thus, FLCMs present a fascinating class of self-supporting carbon electrode materials for EDLCs.