This article reviews recent studies on preparation of layer-by-layer assembled multilayers by stepwise chemical bond formation on the surface. Coordination reactions are useful to synthesize oligomeric and polymeric molecular wires with the desired number of complex units and with the desired physical structures. Regarding the electrode films of redox molecular wires of bis(terpyridine)metal complex oligomers we have prepared, its electrochemical analysis reveals that these redox films with ordered molecular wire structures showed through-bond redox conduction behaviors.
SOFC systems require heat exchange devices to preheat the air, and usually the pre-heater becomes an encumbrance in downsizing. We present a new concept of a honeycomb SOFC which has air-preheating channels. In this SOFC, some honeycomb channels are used for preheating the air, and for cooling the cell stack. In this study, a quasi two-dimensional model was developed to calculate the temperature distribution and the power generation characteristics for H2 fuel. The temperature distributions along the gas flow direction were calculated and the cooling effects of the preheating air were discussed with an adiabatic condition. It was revealed that the air was preheated homogeneously, and the co-flow mode is more effective in preheating the air than the counter-flow mode. Because the spatial variation of temperature in the honeycomb walls was slight, the proposed honeycomb structure with air-preheating channels is expected to be effective in reducing the thermal stresses in high power density SOFC stacks. The result of the simulation also indicated that the power generation characteristics with co-flow condition were better than those with counter-flow condition.
A Pd/MnO2 catalyst was used as the anode materials of an intermediate-temperature Solid Oxide Fuel Cell (SOFC) for direct utilization of dimethylether (DME) gas fuel. The Pd/MnO2 catalyst had morphology that nano Pd particles were dispersed on a manganese oxide with meso-scaled pores. A proton conducting oxide BaCe0.8Y0.2O3−δ was used as the electrolyte (thickness 500 µm) and a Pt was used as the cathode. The cell was operated at 600°C. Maximum power density of the cell using Pt-Pd/MnO2 anode (Pd/MnO2 content of 16.6 wt.%) was 21 mW cm−2 at 50 mA cm−2, while the cells using Pt and Pd/MnO2 as anode materials exhibited maximum power densities of 9 and 10 mW cm−2 at 20 mA cm−2, respectively.
In order to investigate the property, electronic and crystal structures, thermodynamic stability, and cathode performance of Lix(Mn, Co, Ni, M)O2 (M=Al, Ti, Fe) as a cathode active material for Li secondary batteries, LiMn0.3Co0.3Ni0.3M0.1O2 (M=Al, Ti, Fe) and LiMn1/3Co1/3-0.1Ni1/3Al0.1O2 were prepared by the solution method and solid-state method. These materials have the same layered structure (R¯3m) as the LiMn1/3Co1/3Ni1/3O2. Lix(Mn, Co, Ni, Al)O2, which was obtained by the solution method, had a higher discharge capacity and better cycle performance than that obtained by the solid-state method. Based on the results of the electronic and crystal structures, the change in the covalent bond and cation mixing were small by substitution. The enthalpy change per mol of atoms for the reaction, ΔHR, was calculated from the heat of dissolution. ΔHR increased with the decreasing Li content and LixMn1/3Co1/3-0.1Ni1/3Al0.1O2, which was obtained by the solution method, was more thermodynamically stable than that obtained by the solid-state method irrespective of the Li content. LixMn1/3Co1/3Ni1/3O2 is more thermodynamically stable than Lix(Mn, Co, Ni, Al)O2, which was obtained by the same synthesis method. It was suggested that the structural and thermodynamic stability should provide an effective cycle performance.
We reported that carbon black modified with cobalt and various transition metal ions (M) incorporated in a polypyrrole film (Co+MPPy/C) were good electrocatalysts for the reduction of oxygen (O2). After heat treatment of the catalysts at 600 to 650°C under argon atmosphere, which were prepared using with iron and iridium ions as M, the resulted catalysts gave rise to the reduction of O2 at a remarkably positive potential (Ep>0.40 V vs SCE). Rotating ring disk voltammetry (RRDV) revealed that Co+IrPPy/C reduced O2 completely with four electrons (nav=4.0). X-ray photoelectron spectroscopy and X-ray diffraction indicated that the cobalt and M ions were coordinated with nitrogen as the donor atoms and the active sites were maintained even after the heat treatment under argon atmosphere without aggregation of metals and formation of alloys.
The biocompatible composite membranes consisting of hydroxyapatite (HAp) and proton-conductive polymers such as poly (2-acrylamido-2-methylpropane sulfonic acid) (PAMPS), poly styrene sulfonic acid (PSSA), and Nafion® were prepared. High mechanical stability was given to the composite membranes by needle-like HAp crystallites deposited by a setting reaction of calcium phosphate cement. The proton conductivity of composite membranes was strongly influenced by distribution of HAp and polymer, and changed in the range from 8.7×10−3 S cm−1 to 4.5×10−4 S cm−1 at 30°C under 95% relative humidity. The H2–O2 fuel cell based on the PAMPS composite membrane exhibited a promising performance of 20 mA cm−2 at 0.5 V and 30°C as a candidate for the micro-fuel cells for biocompatible devices.
Electroreduction of α-alkylated styrenes (1) in the presence of diphenyl succinate (2) or glutarate (3) in N,N-dimethylformamide (DMF) using an undivided cell equipped with Zn plates as the anode and the cathode brought about regio- and stereoselective efficient double carbon-carbon bond formation between the two olefinic carbon atoms of 1 and one carbonyl carbon atom of 2 or 3, followed by lactonization to give the corresponding five- (4) or six-membered spiro-lactones (5) possessing cyclopropane rings in moderate to good yields.