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The concept of a proton conducting, methanol impermeable composite electrolyte system is demonstrated. A three-layered laminar electrolyte consisting of a dense, methanol impermeable protonic conductor sandwiched between proton permeable electronically insulating layers permits the selective transport of protons while eliminating methanol crossover to the cathode. We demonstrate the selectivity of the composite electrolyte using palladium foil sandwiched between two Nafion TM polymer membranes. The open-circuit voltage for an Ha/O2 fuel cell utilizing this composite electrolyte is unaffected by introduction of methanol to the H2 fuel stream, whereas conventional polymer electrolyte cells suffer severe degradation of performance due to methanol crossover.Research toward the development of low temperature (80-120~ direct methanol fuel cells (DMFCs) has primarily relied on the use of proton exchange membranes such as Nafion TM as the electrolyte. A serious drawback with these polymer electrolytebased DMFC systems is that methanol diffuses through the polymer electrolyte to the cathode, degrading cell performance. Attempts to produce polymeric electrolytes that selectively transport protons, but not small organic molecules such as methanol, have met with very limited success. 1We demonstrate here an alternative approach, a barrier concept, to the prevention of methanol crossover in DMFCs. In this design, a film of a methanol impermeable protonic conductor (MIPC), such as a metal hydride, is sandwiched between proton permeable electronic insulators, such as Nafion TM, forming a composite electrolyte. 2 Although highly permeable, inexpensive metal hydrides, such as surface modified V-15Ni-0.05Ti are known (3 • 10 -8 mol HJm s Pa ~/2, 423 K), Pd (2 • 10 9 mol H2/m s Pa ~]2, 423 K) 3 is used here as a model barrier phase; the close-packed structures of metal hydrides prevent permeation of larger molecules such as methanol and water. A hydrogen loaded palladium (palladium hydride) foil can be viewed as a proton permeable membrane: reductive adsorption of protons occurs on the surface facing the fuel anode, hydrogen diffuses through the palladium, and hydrogen atoms on the surface facing the oxygen cathode are oxidatively desorbed as protons (Fig. 1). By appropriately activating the surface of the MIPC+ the kinetics of hydrogen exchange can be markedly improved.

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Anode-supported planar solid oxide fuel cells (SOFC) were fabricated by a single step co-firing process. The cells were composed of a Ni + yittria-stabilized zirconia (YSZ) anode, a YSZ electrolyte, an industrial Ca-doped LaMnO3 (LCM) (or lab-made LCM) + YSZ cathode active layer, and an industrial LCM (or lab-made LCM) cathode current collector layer. The fabrication processes involved tape casting of the anode, screen printing of the electrolyte and the cathode, and one step co-firing of the green-state cells at 1300°C for 2h . The performance of the cells was greatly improved by optimization of these materials and fabrication processes. The electrochemical performance tests of these cells showed that they could provide a stable power density of 0.2– 1.0W∕cm2 with hydrogen as fuel and air as oxidant while operating in the temperature range 700– 900°C . The effects of various polarization losses including ohmic polarization, activation polarization, and concentration polarization were studied by impedance spectroscopy measurements and curve-fitting experimentally measured voltage vs current density traces into an appropriate model. Based on these measurements and curve fitting results, the relationships between cell performance and various polarization losses and their dependence on temperature and microstructure, were rationalized.

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Ag-NPs doped NiFe 2 O 4 (NFO) thin films have been synthesized by the chemical solution deposition method. The effect of Ag-NPs incorporation on the resistive switching (RS) properties of NFO films with different doping concentrations in the range of 0 to 1.0% Ag was investigated. Results show that Ag-NPs doped NFO based memory devices perform resistive switching with much better uniformity and repeatability in switching cycles, and have excellent reliability at an appropriate Ag-NPs doping concentration (i.e. 0.5%) instead of very low and high doping concentrations (i.e. un-doped NFO film, 0.2% and 1.0% Ag). On the basis of analyses performed on current-voltage characteristics and their temperature dependence, it was found that the carrier transport occurred through the conducting filaments in the low resistance state with ohmic conduction, and in the high resistance state with Schottky emission. In addition, the temperature dependence of the resistance and magnetic behavior at HRS and LRS revealed that the physical origin of the RS mechanism, which involves the formation and rupture of the conducting paths, consists of oxygen vacancies and Ag atoms. Ag-NPs doping-induced changes in the saturation magnetization, associated with resistive switching, have been ascribed to variations in the oxygen vacancy concentration. The excellent endurance properties (>10 3 cycles), data retention (of >10 5 s at 298 and 358 K), and good cycle-to-cycle uniformity are observed in 0.5% Ag-NPs doped NFO-based memory devices.

A metal-free synthesis of aryltriphenylphosphonium bromides by the reaction of triphenylphosphine with aryl bromides in refluxing phenol is developed. This reaction tolerates hydroxymethyl, hydroxyphenyl, and carboxyl groups in aryl bromides, allowing to synthesize multifunctional aryltriphenylphosphonium bromides, from which facile access to multifunctional aryldiphenylphosphines and their oxides by hydrolysis and subsequent reduction is exemplified. A two-step addition–elimination mechanism, with the elimination step being a fast step, is also proposed.

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