This study was performed to investigate the effect of grain size on crystallographic structure and electrochemistry properties for nanocrystalline La0.8Sr0.2Co1-xFexO3 (x = 0.1 and 0.9) powders, as a suitable model for SOFC cathodes. Different sets of perovskite-type mixed oxides were successfully prepared by the amorphous citrate method. A particle size dependent modification in the lattice parameters of La0.8Sr0.2Co1-xFexO3 nanocrystalline powders was observed. Clear correlations between crystal size, oxygen content, crystallographic structure, and electrochemical performance were observed

A single step co-firing process for fabricating solid oxide fuel cells (SOFCs) requires refractory electrodes to prevent excessive sintering of the electrode while facilitating full-density sintering of the electrolyte. Single cell current-potential curves and impedance measurements indicate that the majority of the performance losses occur in the cathode and are due to activation polarization. A-site deficient calcium and cerium doped lanthanum ferrite cathode powders were synthesized and investigated as possible refractory cathode materials with low activation polarization losses. Four-probe conductivity measurements indicated that all compositions were suitable as cathodes. However, reactivity with YSZ reduced the conductivity by as much as two orders of magnitude, too low for use as a cathode. These refractory cathode compositions could be effective if a suitable barrier layer is applied to prevent reaction with YSZ. Experiments will investigate the applicability of a doped-ceria barrier layer to prevent reaction between the lanthanum ferrite cathode layer and the YSZ electrolyte layer.

We have synthesized spinel LiMn1.99Nd0.01O4 and LiMn1.99Ce0.01O4 powder by chemical synthesis method. The synthesized powders were used to prepare cathodes for Li ion coin cells. The structural and electrochemical properties were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry and charge-discharge studies, respectively. The cyclic voltammetry of the cathodes revealed the reversible nature of Li-ion intercalation in the cell. The charge-discharge characteristics for LiMn1.99Ce0.01O4 were obtained in 3.5 V – 4.8 V voltage range, while for LiMn1.99Nd0.01O4 the charge-discharge were carried out in 3.4 V – 4.4 V range. The initial discharge capacities of LiMn1.99Ce0.01O4 and LiMn1.99Nd0.01O4 were obtained as 134mAh/g and 149 mAh/g, respectively. The coin cells were tested for up to 25 charge-discharge cycles and after 25 cycles the discharge capacities were determined to 79.5 mAh/g and 132 mAh/g for LiMn1.99Ce0.01O4 and LiMn1.99Nd0.01O4 cathodes respectively. However, by doping with a small concentration of rare earth materials, like Ce and Nd reduces the capacity fading in pure LiMn2O4 cathodes making it suitable for Li-ion battery applications.

The cathode performances of perovskite-type oxide electrodes were investigated in the H2-O2 fuel cell with proton-conducting electrolyte. Among the perovskite-type oxides tested in the present study, La1-xSrxFeO3(LSFO) showed the best cathode performance. The cathode performances of LSFO depended on the Sr content and the heat-treatment temperature prior to electrochemical measurements. The cathode reactions of both LSFO and Pt electrodes are discussed briefly based on the cathode overpotentials measured as a function of oxygen partial pressure. Finally, the structure and the electrical conductivity of the proton-conducting ceramic film fabricated on LSFO electrode substrate are presented.

The concept of reversible and non reversible conversion in high bandgap metal fluorides is expanded through the introduction of mixed conducting matrices to form dense nanocomposite structures capable of good transport to nanodomains of metal fluorides. Specific examples for BiF3 and especially CuF2 using matrices of nominal composition of MoO3 are discussed. The reversible conversion mechanism of the metal halides is expanded to enable a new concept of electrochemically self assembled microbatteries (ESAMs) based on alkali halides. Such technology enables the fabrication of a solid state microbattery between two current collectors of various configurations on the microscale. First examples demonstrated based on LiI have demonstrated cell formation, appreciable energy density, and preliminary reversibility.

Effect of fluorite-like or perovskite-like complex oxide promoters and Pd on the performance of Ni/YSZ and Ni/ScSZ cermets in methane steam reforming or selective oxidation by O2 into syngas at short contact times was studied. Spatial uniformity of dopants distribution in composites was controlled by TEM combined with EDX, while the lattice oxygen mobility and reactivity was elucidated by CH4 and H2 TPR. Oxide promoters allow to operate even at stoichiometric H2O/CH4 ratio by suppressing coke deposition through modification of Ni surface, while doping by Pd ensures reasonable performance at moderate (∼550 °C) temperatures required for Intermediate–Temperature Solid Oxide Fuel Cells (IT SOFC).

Rietveld analysis for the time of flight powder neutron diffraction profile for LiFePO4 at room temperature was performed. Refined tensor elements of the unisotropic thermal factor under the elliptic approximation showed the principal axis of the lithium vibration is toward the face shared vacant tetrahedral space and is consistent with the theoretical prediction; lithium ions diffuse along curved one-dementional chain along b-axis. Impact of temperature on the phase diagram of LixFePO4 with > 200nm particle size was slight under the unmixing line around 200 C. While the reduction in particle size down to <100 nm seems to have significant effect to the room temperature miscibility gap. The thermodynamic concepts for the extended solution in smaller particles are discussed, followed by a demonstration of very high rate capability observed for the small spherical particles < 80 nm.

Barium zirconate BaZr0.8Y0.2O3-δ, to be used as protonic conductor under hydrogen containing atmosphere in intermediate temperature (500-700°C) solid oxide fuel cells (IT-SOFCs) was prepared using a sol-gel technique to produce materials with controlled chemical structure and microstructural properties. Several synthetic procedures were investigated, dissolving the metal cations in two solvents (water and ethylene glycol) and using different molar ratios of citric acid with respect to the total metal content. A single phase was obtained at temperature as low as 1100°C. To verify the chemical stability, all the sintered oxides were exposed to CO2 and the phase composition of the resulting specimens was investigated using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). Fuel cell polarization curves on symmetric Pt/BZY20/Pt cells of different thickness were measured at intermediate temperatures (500-700°C).

Nanocrystalline powders of Y2-xPrxRu2O7 were prepared by a co-precipitation method, and were tested as electrode on ESB and GDC electrolytes by electrochemical impedance spectroscopy in the 300-750°C temperatures range. The electrode polarization was studied as a function of the amount of praseodymium in the cathode material. Both systems, Y2-xPrxRu2O7/ESB and Y2-xPrxRu2O7/GDC, showed a similar variation of the electrode area specific resistance (ASR). Y1.5Pr0.5Ru2O7 cathode material presented the best performance, with ASR value of 0.19 Ωcm2 on ESB and 4.23 Ωcm2 on GDC at 700°C. Furthermore, the change in ASR with the oxygen partial pressure suggested that the rate limiting step is the surface diffusion of the adsorbed oxygen at the electrode surface to the triple-phase boundary. Thus, the low value of resistivity of the Y1.5Pr0.5Ru2O7 in contact with ESB results from a much lower charge transfer resistance compared to the Y2-xPrxRu2O7/GDC system, and a partial solid diffusion at the interface electrode/electrolyte that increases the effective triple phase boundary length. This suggests that Y2-xPrxRu2O7 is a promising material for cathode application in ESB-based electrolyte for intermediate temperature solid oxide fuel cells (IT-SOFCs).

ScCeZrO2 ceramic powders produced by two different manufacturers have been used for the manufacturing of ScCeZrO2 electrolyte based solid oxide fuel cells. Thin, porous anode and cathode layers have been deposited on 150 μm thick, dense electrolyte tapes. Preliminary electrochemical testing of the cells has been performed.

We design a way that the anode hosts provide lithium ion in lithium ion battery operation. If the limiting factors of the cathode materials are less, there will be more alternatives for it. It was proven to be successful by two kinds of test cells based on LixCn as anode material, and β-FeOOH or Cr8O21 as cathode materials. Their theoretical capacities are much higher than those present electrode materials. Unlike the lithium secondary batteries with lithium metal foil or lithium alloy as anode, this type of lithium ion batteries with LixCn as anode prohibit dendrite formation during charging-discharge process. The idea of lithium ion sources coming from the anode can come true successfully as a result that steady protecting solution be sought for LixCn.

Electrochemical sensors for Volatile Organic Compound (VOCs) based on commercial YSZ layers were fabricated using Pt as reference electrode and SmFeO3 perovskite oxide as a sensing electrode, both exposed to the same gas environment. Pt was sputtered on YSZ layers while SmFeO3 p-type semiconducting oxide was deposited by electrophoretic deposition (EPD). Nanometric SmFeO3 oxide powders were selected because they have already shown good sensing performance in semiconducting sensors for oxidizing gases such as NO2 and ozone, and reducing gases, such as VOCs. Potentiometric measurements were performed under exposure to different concentrations of VOCs such as: methyl ethyl ketone (MEK), ethanol (EtOH) and acetic acid (AA). The best gas sensing response was obtained at 400°C.

One of current trends of the PEM research is the development of new membranes working at high temperature and low humidity.

Acid-doped polybenzimidazoles are particularly appealing because of high proton conductivity without humidification and promising fuel cells performances. PBI contains basic functional groups that can easily interact with strong acids, such as H3PO4, H2SO4, allowing proton migration along the anionic chains via a Grotthuss mechanism.

In this work phosphoric acid-doped membranes, synthesised from benzimidazole-based monomers with increased basicity and molecular weight, are described and discussed. The influence of the monomer structure on the transport properties and on the physico-chemical interactions between acid and polymer has been investigated by means of impedance spectroscopy and 31P solid-state NMR. Test of methanol crossover and diffusion have been performed to check the membrane suitability for DMFCs.

An electrochemical cell employing a YSZ electrolyte and two Au electrodes was utilized as a model system for investigating the mechanisms responsible for impedancemetric NOx (NO and NO2) sensing. The cell consists of two dense Au electrodes on top of a porous/dense YSZ bilayer structure (with the additional porous layer present only under the Au electrodes). Both electrodes were co-located on the same side of the cell, resulting in an in-plane geometry for the current path. The porous YSZ appears to extend the triple phase boundary and allows for enhanced NOx sensing performance, although the exact role of the porous layer is not completely understood. Impedance data were obtained over the frequency range of 0.1 Hz to 1 MHz, and over a range of oxygen (2 to 18.9%) and NOx (10 to 100 ppm) concentrations, and temperatures (600 to 700 °C). Data were fit with an equivalent circuit, and the values of the circuit elements were obtained for different concentrations and temperatures. Changes in a single low-frequency arc were found to correlate with concentration changes, and to be temperature dependent. In the absence of NOx , the effect of O2 on the low-frequency resistance could be described by a power law, and the temperature dependence described by a single apparent activation energy at all O2 concentrations. When both O2 and NOx were present, however, the power law exponent varied as a function of both temperature and concentration, and the apparent activation energy also showed dual dependence. Adsorption mechanisms are discussed as possibilities for the rate-limiting steps.

Zinc oxide and cobalt hydroxide films with ordered lamellar structures were electrochemically produced via interfacial surfactant templating. This method utilizes interfacial amphiphile assemblies on a working electrode as a template to electrodeposit inorganic nanostructures. Surfactants with anionic head groups (e.g. sodium dodecyl sulfate, 1-hexadecanesulfonate sodium salt, dodecylbenzenesulfonate sodium salt, and dioctyl sulfosuccinate sodium salt) formed bilayer assemblies with Zn2+ and Co2+ ions on the working electrode and guided the lamellar growth of ZnO and Co(OH)2 films. In order to gain the ability to precisely tailor inorganic lamellar structures, the effect of co-solvent and type of working electrode on the repeat distances, homogeneity and orientation of the interfacial amphiphilic bilayers were investigated. The results described here will provide a useful foundation to design and optimize synthetic conditions for electrochemical construction of inorganic lamellar structures.

Li4+xTi4O12 and Li1-yMn2O4 materials have been respectively prepared by a chemical lithiation of Li4Ti4O12 in the presence of an excess of butylithium (LiC4H9) in hexane solution and chemical delithiation of LiMn2O4 spinel using NO2BF4 oxidizer in an acetonitrile medium. The thermal gravimetric results show that Li1-yMn2O4 releases oxygen starting from 200°C with an overall oxygen loss of 6 wt% at 500 °C, whereas Li4+xTi4O12 gains oxygen starting from 200 °C with an overall oxygen gain of 4 wt % at 500 °C. The reactivity of the Li4+xTi4O12 and Li1-yMn2O4 powders in the presence of electrolytes was investigated by a differential scanning calorimetry (DSC) between room temperature and 375°C, and compared to a lithiated graphite in the case of the Li4+xTi4O12 negative electrode material.

We have fabricated a solid oxide fuel cell (SOFC) using BaCe0.8Y0.2Ox (BCY) proton conductor as the electrolyte. An ≈ 15-μm-thick dense BCY film was prepared on a porous Ni/BCY cermet (i.e., ceramic/metal composite) substrate by a colloidal spray deposition technique. The gas permeable Ni/BCY cermet substrate backed with nickel mesh was used as the anode, and platinum paste backed with platinum mesh served as cathode. The current-voltage characteristics of the BCY-based SOFC were measured in the temperature range 600-800°C using wet air on the cathode side and wet hydrogen on the anode side. The open circuit voltage was close to the theoretical value at all operating temperatures. The power density of the fuel cell was ≈240 and ≈875 mW/cm2 at 600 and 800°C, respectively.

In the study Li4/3Ti5/3O4 thin films were deposited on Pt substrates by sol-gel method using a spin coator. The coated films are dried at 310-360 °C, and then annealed at 500-800 °C for 30min. The prepared films were characterized by X-ray diffraction, atomic force microscope and scanning electron microscope. The results indicated that the prepared film belonged to a spinel structure and had a uniform morphology. Electrochemical properties of the prepared electrode films were evaluated by using a discharge and charge test. From these results, it can be showed that the thin film electrode annealed at 700 °C exhibited good crystallinity, smooth surface morphology, high capacity, and good rechargeability. Therefore, This film was therefore suitable for use as an anode for thin-film microbatteries.

An impedancemetric technique for NOx sensing using a yttria-stabilized zirconia (YSZ) electrochemical cell is reported. The cell consists of a dense YSZ substrate disk with two YSZ/metal-oxide electrodes deposited on the same side. The cell is completely exposed to the test gas (no air reference). The NOx and O2 response of the cell were evaluated during constant-frequency operation at frequencies in the range from 1 to 1000 Hz. At 10 Hz, the NOx response (as measured by phase angle shift) is shown to be linear with concentration over the range from 8-50 ppm, with comparable response to both NO and NO2. A method of operation is described which enables compensation for the O2 response at oxygen concentrations greater than approximately 4%. This mode of operation allows the sensor to provide sub-10 ppm detection of NOx irrespective of the O2 concentration. The sensor exhibits good stability during continuous operation for more than 150 hr. It was observed that the O2 response of the cell may be too slow to be of practical use, taking several minutes to equilibrate after changing the concentration by a few percent. However, data will be presented which demonstrate that this response is related to the metal oxide used for the electrode, and that more rapid response times can be achieved by modification of the electrode material.

Lithium batteries have found a wide range of applications due to their very compact energy packing and effective cost. Theoretically Li-cells can hold up to 5V, however to date no mass-produced rechargeable battery surpasses 4 V. The structure here analyzed consists of: lithium porous cathode, solid electrolyte and silver anode. A spinel LiNi0.4X0.1Mn1.5O4 sol-gel layer was deposited on a porous substrate in order to obtain higher specific surface for single chips. The anode was thermally evaporated Ag. The electrolyte used was a sol-gel hybrid layer containing Li ions. The devices, fabricated on ceramic wafers, displayed high capacities.