A tremendous variation in electrical resistance, from the semiconductor to metallic range, has been observed in titania nanotube arrays at room temperature, ≈25°C, in the presence of low ppm hydrogen gas concentrations (≤ 1000 ppm). The nanotube arrays are fabricated by anodizing titanium foil in an aqueous fluoride containing electrolyte solution. Subsequently, the arrays are annealed in an oxygen ambient, then coated with a 10 nm layer of palladium by evaporation. Electrical contacts are made by sputtering a small (e.g. 1 mm diameter) platinum disk atop the Pd coated nanotube-array. These sensors exhibit a resistance variation of the order of over 107 (1,000,000,000%) in the presence of 1000 ppm hydrogen at 23°C. To the best of our knowledge this dynamic change in electrical resistance the largest known response of any material, to any gas, at any temperature. The sensors demonstrate complete reversibility, repeatability, high selectivity, no drift and wide dynamic range. The nanoscale geometry of the nanotubes, in particular the points of tube-to-tube contact, is believed to be responsible for the outstanding hydrogen gas sensitivities.

We report a process for the successful incorporation of ceria in to yttria-stabilized zirconia (YSZ) columnar nanostructures grown by glancing angle deposition (GLAD) technique, resulting in high interface density columnar nanostructures. The incorporation of ceria into YSZ columns is confirmed by scanning electron microscopy (SEM) in a cross sectional geometry with in-situ analysis of elemental x-ray mapping technique and energy dispersive x-ray analysis (EDX). Controlled engineering of such nanostructures is potentially important in the future development of high efficiency solid oxide fuel cell electrolytes. The challenges and advantages of this process are discussed.

A family of Co-free, Fe/Mn-based perovskite-type oxides, (Sr, A')(Fe, Mn)O3-δ (A'=La, Ba, Ca), was synthesized, and their oxygen permeability and phase stability in reducing atmosphere were investigated. The substitution of Mn at B site caused the decrease in oxygen permeability. As for the effect of A-site substitution, prominent promotion was observed by the substitution of Ba for 30% of Sr, and Ba0.3Sr0.7FeO3-δ was found to be one of most excellent oxygen permeable materials with the permeation flux of 3.0 cm3(STP) cm−2 min−1 at 900 °C. Reduction tolerance was evaluated by TG measurements in a 5%H2/N2 stream up to 1000 °C. After the TG measurements, crystal structures of La-Sr-Co-Fe-O and Sr-Fe-(Mn)-O perovskites were decomposed or transformed into low oxygen permeable phases, but the perovskite-type structure of Ba-Sr-Fe-(Mn)-O survived. The Fe/Mn-based perovskites with high oxygen permeability and exceeding reduction tolerance could be used as stable membrane materials for membrane reactors catalyzing NO-CH4 reaction and the partial oxidation of CH4 into synthesis gas.

The multi-walled carbon nanotubes (MWNTs) prepared by CVD were used in electrochemical intercalation reaction with Li+. The results of the first several charge-discharge cycles showed that the reversible capacity of the MWNTs was larger than the theoretical capacity of graphitized carbon. The equivalent circuit of the Li+ intercalated into the MWNTs was simulated The diffusion coefficient calculated based on the results of the impedance was in the range between 1 ∼ 4×10−10 cm2s−1. The diffusion coefficient calculated based on the technique of the chronoamperometery was 3.5×10−10 cm2s−1. The diffusion coefficients of the Li+ reacted with MWNTs was in the range of that of the most carbon materials. Using EMF method the partial molar entropy (ΔSx) and partial molar enthalpy (ΔHx) of the Li+ intercalated into the MWNTs were calculated as a function of × in Lix C6 at different temperatures. The values of ΔSx were in the range of 150 ∼ 550 J mol-1K-1. The values of ΔHx at 35 °C were in the range of 40∼110 kJ mol−1. Both of the ΔSx and ΔHx were lower and the changes were smaller than the values of some other carbonaceous materials. By analyzing the results conclusion is obtained that Li+ exist in MWNTs with different types which include adsorption and intercalation types.

La1.61GeO5 thin film was fabricated on porous NiO-Ce0.80Sm0.20O2-δ (SDC) substrates by pulsed laser deposition (PLD) under various deposition conditions and the deposition parameters were optimized for obtaining the dense La1.61GeO5-δ film for the electrolyte of SOFC. It has been found that the high substrate temperature and the low oxygen pressure in chamber are suitable for obtaining the dense La1.61GeO5-δ thin film on porous NiO-SDC anode substrate. Since the as-deposited film is amorphous state, post-anneal treatment is essential for obtaining the crystalline La1.61GeO5-δ film. Under the optimized deposition condition, a dense and La1.61GeO5-δ thin film with a thickness of 3 μm can be successfully obtained. The obtained La1.61GeO5-δ film exhibits the electromotive force, which is slightly smaller that that of the theoretical open circuit potential. The power generation property of the cell using the obtained La1.61GeO5-δ film was studied and it was found that the maximum output density of a SOFC single cell using a La1.61GeO5-δ thin film deposited on a porous NiO-SDC substrate reached to 1948.2 mW/cm2 at 1173 K and 424.4 mW/cm2 at 873 K.

In the present work, an electrochemically driven ceramic oxygen generator (ECOG) device is investigated. The present device is based on an electrode supported architecture. Structural and electrochemical characterizations of the electrochemical cell have been carried out. The O2 production rate has been measured showing a performance four times higher than the generally accepted targets for practical applications. The high performance obtained with this device, indicates that there are good perspectives to decrease the O2 production costs significantly decreased as well as small and light weight devices for portable uses are envisaged.

Dramatic improvement in the selective separation and purification of NOX in exhaust gases by an electrochemical reactor with a catalytic electrode has been achieved. The novel electrochemical cells for NOX decomposition were developed by nano-scale control of penetrating pores from the catalytic electrode surface to the bottom of the catalytic electrode layer. The penetration pores and nano-size Ni grains are self-assembled at NiO/YSZ interfaces in the catalytic electrode by oxidization-reduction reaction of the NiO during the cell operation. In order to use reduced Ni for NOX decomposition reaction efficiently, we successfully designed a functional multilayer catalytic electrode. By multilayering of the catalytic electrode, adsorption and decomposition of coexisting oxygen in exhaust gases was suppressed and the selectivity of NOX decomposition reaction is improved. Structural change of the catalytic electrode as a result of the electrochemical processes was investigated and correlated with the NO decomposition properties of the cell.

The lithium extraction rate and the rate capability of layered LiNi0.5–0.5yMn0.5–0.5yCoyO2 with 0 ≤ y ≤ 1 have been investigated, respectively, by chemically extracting lithium with the oxidizer NO2BF4 in acetonitrile medium and electrochemically discharging at various C-rates. Both the chemical lithium extraction rate and the electrochemical rate capability are found to increase with increasing Co content y in LiNi0.5–0.5yMn0.5–0.5yCoyO2. While no clear relationship is seen between electrical conductivity and the rate capability, increasing cation disorder between the lithium and transition metal planes with decreasing Co content is found to decrease the chemical lithium extraction rate and rate capability. The lithium extraction rate also influences the structure (P3 vs O1 vs O3) of the end members Ni0.5–0.5yMn0.5–0.5yCoyO2-δ obtained by extracting all the lithium with 100 % excess NO2BF4 in an acetonitrile medium.

The H+-ion treatment effect on TlH2PO4, a KH2PO4 (KDP)-type ferroelectrics, was studied by nuclear magnetic resonance (NMR) and AC dielectric measurements. A sample of TlH2PO4 was irradiated by 1-MeV H+ ion beams to a dose of 1015 ions/cm2. The irradiation changed the hydrogen-bond geometry, presumably affecting the order-disorder proton dynamics. The deformation of the PO4 tetrahedra was identified by the isotropic chemical shift and the full width at half maximum (FWHM) of the high-resolution 31P NMR spectra. A prominent decrease in the dielectric constant was also observed after the irradiation. The macroscopic and microscopic changes due to the irradiation are discussed in the light of the proton dynamics.

This work presents results of studies of the structural features of nanocrystalline doped Ce1−xMexO2−y samples (Me = Sm, Bi, Gd; X = 0–0.5) prepared via the polymerised precursor (Pechini) route by using a combination of diffraction (XRD, TEM, WAXS on SR) and spectroscopic (EXAFS, Raman, FTIRS of lattice modes, XPS, SIMS) methods.

Nanometric pyrochlore lead ruthenate (Pb2Ru2O6.5) powders were prepared using a new chemical route as a possible candidate for cathode materials in solid oxide fuel cells (SOFCs). Pb2Ru2O6.5 was mixed with yttria-stabilized zirconia (YSZ) and erbia-stabilized bismuth oxide (ESB) to fabricate porous composite electrodes. Pure pyrochlore or composite electrodes were deposited as thick films onto YSZ and ESB electrolytes. Powders and films were analyzed using X-ray diffraction (XRD) analysis and field emission scanning electron microscopy (FE-SEM). Electrochemical features of the electrodes were investigated using electrochemical impedance spectroscopy (EIS) measurements at different temperatures in air for symmetric cells. The composite electrodes were compared to single Pb2Ru2O6.5 phase electrodes to evaluate the effect on polarization of the addition of the pure ionic conductor phase in the electrodes.

A simple organic solvent based sol-gel method for synthesis of carbon-coated LiFePO4 is developed. Phase pure LiFePO4 with uniform size of 200–300 nm and no agglomeration is obtained, with 1.8 wt % surface carbon formed in-situ. Such a material gives specific discharge capacities of 150 mAh/g and 145 mAh/g at C/5 and 2C at room temperature, respectively, with desirable cycling stability. The dependence of particle size and morphology on precursor concentrations is opposite to conventional solution based methods. Other LiMPO4 (M = Mn, Co, Ni, etc) with favorable physical characteristics can be synthesized the same way.

Average Li intercalation potentials were calculated for lithium-4d-transition-metal-oxides. The effect on the intercalation voltage of metal substitution was systematically studied by altering the 4d transitional metals M (M= Mo, Nb, Rh, Zr, Ru) in LiMO2 in the α-NaFeO2 structure. Lattice parameters in the layered α-NaFeO2 structure computed in the GGA approximation are in reasonable agreement with experiment. The intercalation potentials and relative formation energies of the fully lithiated LiNi1/3Mn1/3Mo1/3O2, fully delithiated Ni1/3Mn1/3Mo1/3O2 and the intermediate phases, Li1/3Ni1/3Mn1/3Mo1/3O2 and Li2/3Ni1/3Mn1/3Mo1/3O2, were computed by employing a generalized alloy theory. A minute substitution of cationic Mo in LiNiMnO2 was experimentally investigated to examine the effect of the Mo substitution on the electrochemical properties.

The Mössbauer spectroscopy is an efficient experimental tool to study lithium insertion mechanisms in negative electrodes of Li-ion batteries at the atomic scale. However, a quantitative interpretation of the experimental data is often difficult due to the complexity of the spectra and we propose to use first-principle calculations of the hyperfine parameters. Three different types of negative electrode materials are considered. First, the experimental 119Sn Mössbauer spectrum obtained for the insertion of 3.5 Li into SnO is compared to the theoretical spectrum, which clearly establishes the existence of Li-Sn stable phases. Then, the analysis of the 121Sb Mössbauer spectra for metal antimonides at the end of the first discharge shows different behaviours depending on the lithium rate. Finally, tin and iron doped titanates are considered to study changes in Ti local environments during lithium insertion.

The oxide-ion conduction of gadolinium zirconate - titanates, Gd2(Ti1−xZrx)2O7 (GTZ), has been investigated under high pressure in the range of 2 to 6 GPa with the aid of a cubic-anvil-type apparatus. For these pyrochlore compounds, the oxide-ion conductivity at elevated temperatures in the range of 750 to 960 °C decreased with increasing pressure, indicating the presence of a positive activation volume, ΔV. The activation volumes ΔV of GZ (x = 1.0) and GTZ (x = 0.95) were 2.0 and 1.3 cm3/mol, respectively, at 750 °C and decreased with increasing temperature.

Ce0.8Gd0.2O1.9 (CGO) - MFe2O4 (M=divalent cation) is a composite-type oxygen-ionic and electronic mixed conductor. Dense nanocrysalline CGO-CoFe2O4 thin films with a thickness of approximately 1 μm were prepared on CGO porous substrates by a chemical solution spin-coating method. The oxygen permeable flux of the thin film was investigated in temperature range of 700°C - 800°C without physical leak of N2 gas. The permeable flux depends on the measuring time, when the measuring temperature was kept at 750°C before increasing to 800°C. This fact suggests that the O2 permeable properties were affected by a slight change of the film morphology and the crystallinity.

Nanostructured Platinum-based electrode catalysts were prepared via in-situ colloidal impregnation for polymer electrolyte fuel cells. Crystallite size, grain size, and distribution of Pt nanoparticles on carbon support materials were characterized by XRD, TEM, high-resolution FESEM, and STEM. Effective surface area and kinetically-controlled current density of Pt electrode catalysts were analyzed by cyclic and hydrodynamic voltammetry using rotating disk electrodes. PEFCs with these electrode catalysts were also prepared and their I-V characteristics were examined at 80°C.

We have succeeded to develop Pt electrode catalysts with a diameter of a few nm, supported on carbon nanofibers with different structures (including herringbone-type fibers, platelet-type fibers, and highly-conductive vapor-grown fibers), carbon nanotubes, as well as carbon black. The dependencies of nanostructure and electrochemical properties on crystallographic structure of carbon support materials and preparation conditions of electrode catalysts are analyzed and discussed. Nanostructural design of PEFC electrode catalyst layers using carbon nanofibers as catalyst supports and electrode fillers is also discussed.

To increase electrode cycling performance in batteries, most researchers generally focus their work on the active material optimisation. Here we show that the polymeric binder of the composite electrode may have an important role on the electrode performance. We describe a new tailored polymeric binder combination with controlled polymer-filler (carbon black) interactions that allows the preparation of new and more efficient electrode architecture. Using this polymeric binder, composite electrodes based on Li1.2V3O8 display a room-temperature cycling capacity of 280 mAh/g (C/5 rate, 3.3–2 V) instead of 150 mAh/g using a standard-type (PVdF-HFP binder) composite electrode. We have coupled SEM observations, galvanostatic cycling and electronic conductivity measurements in order to define and understand the impact of the microstructure of the composite electrode on its electrochemical performance.

Layered Li1+x(Ni0.425Mn0.425Co0.15)1−xO2 materials (x = 0 and 0.12) have been prepared by a coprecipitation method. The substitution of × Li+ ions for × metal ions in the transition metal layers leads to an increase in the average transition metal oxidation state for charge compensation, which was found to be due to the oxidation of Ni2+ ions into Ni3+ ions. The refinement in the R-3m space group of the X-ray diffraction data has shown an increasing lamellar character for the structure of these materials, with increasing overlithiation. Electron diffraction has revealed the presence of a √3.ahex. × √3.ahex. superstructure due to a cationic ordering in the transition metal layers, those being packed with faults along the chex.-axis. From an electrochemical point of view, the reversible capacity in the 2–4.3V decreased with overlithiation, in agreement with a decreasing amount of exchangeable electrons.

This study aims to develop novel polyelectrolytes including lithiated imidazole heterocycles for use in lithium ion rechargeable batteries. Lithium ion local mobility in these materials is characterized by 6, 7Li solid-state NMR. By comparing these results with macroscopic ionic conductivity, measured by impedance spectroscopy, we will be able to develop a picture of the ionic conductivity at the microscopic level. Multinuclear solid state NMR provides information on microscopic interactions including ionic mobility and ring reorientations which govern the efficiency of conductivity. Our research includes 6, 7Li variable MAS NMR studies at intermediate spinning speeds, relaxation investigations to determine spin-lattice relaxation times (T1) of lithium ion hopping, and 2D exchange spectroscopy to determine possible chemical exchange processes. A very long T1 (135 s at ambient temperature) and an activation energy Ea = 17.2 kJ/mol suggests rigid molecule structure and the absence of the ring reorientation of the model compound, lithium imidazolium (LiIm). We compare this to the behavior of LiIm doped with lithium methanesulfonate, which we show to form a new ionic complex with lower T1 and corresponding lower activation energy. With the goal of creating new polyelectrolytes, we have synthesized electrolytes incorporating lithiated imidazole rings, where lithium transport may be independent of polymer-backbone flexibility, and thus polymers with high Tg may be viable. Such materials are highly desirable for secondary lithium polymer battery applications.