Advantages of a Polyimide Membrane Support in Nonhumidified Fluorohydrogenate‐Polymer Composite Membrane Fuel Cells

We have successfully prepared composite membranes consisting of the ionic liquid N‐ethyl‐N‐methylpyrrolidinium fluorohydrogenate and the polymer 2‐hydroxyethylmethacrylate and have secured them on a polyimide (PI) membrane support. The resulting EMPyr(FH)_1.7F–HEMA (9:1 molar ratio) composite possesses ionic conductivity of 75 mS cm⁻¹ at 120 °C when a 16‐µm support is employed, showing improved performance with elevated temperature; this marks a significant difference from devices using conventional polytetrafluoroethylene supports. In the single cell test, a maximum power density of 31 mW cm⁻² is observed at 120 °C. Cross‐sectional SEM images of the corresponding membrane electrode assemblies reveal no significant difference in membrane thickness before and after cell testing, implying that this support does not suffer from membrane softening issues.     

Synthesis of Ca–Co hydroxides and their use in facile fabrication of textured CayCoO2 thermoelectric ceramics

A brucite-type hydroxide of Ca_zCo_1?z(OH)₂ with a high Ca content was synthesized and utilized as a single-source precursor for the fabrication of bulk ceramics of a semiconducting layered calcium cobaltite Ca_yCoO₂. Plate-like Ca_zCo_1?z(OH)₂ particles with z up to 0.22 were reproducibly obtained by a reverse co-precipitation method using KOH as an alkaline source. Uniaxial pressing of the plate-like Ca_zCo_1?z(OH)₂ particles (z?=?0.22), which was calcined at 373?K beforehand, at a pressure as high as 500?MPa produced a highly dense green pellet where the plate-like particles were stacked along the pressing direction. The green pellet was then converted by a heat treatment at 923?K into an oxide ceramic of preferentially (010)-oriented Ca_yCoO₂ via a topotactic-like pyrolytic reaction maintaining edge-sharing CoO₆ octahedra. Although the ceramic also contained a minor insulating Co₃O₄ phase (16.7?±?0.7?mol% estimated from thermal analysis), the electrical measurements proved its p-type semiconducting behavior resulting from the Ca_yCoO₂ phase with enhanced Seebeck coefficient exceeding 160 μV/K at room temperature.     

Structural and optical properties of magnesium nitride formed by a novel electrochemical process

The electrochemical formation of magnesium nitride (Mg₃N₂) films in LiCl-KCl containing Li₃N at 723 K was investigated. From a thermodynamic point of view, a potential-pN³⁻ diagram was constructed for the Mg-N system in an analogous fashion to Pourbaix diagrams for aqueous solutions. As a result, the thermodynamically stable region of Mg₃N₂ in LiCl-KCl-Li₃N was identified. XRD analysis revealed that Mg₃N₂ film was obtained by potentiostatic electrolysis of a magnesium electrode between 0.4 and 0.8 V (versus Li⁺/Li), and the structure of obtained Mg₃N₂ was anti-bixbyite (a = 1.001 nm). Reflectance measurements clarified that assuming direct transition, the bandgap energy was 3.15 eV and assuming indirect transition, the bandgap energy was 2.85 eV.     

An Extremely Active Pt/Carbon Nano-Tube Catalyst for Selective Oxidation of CO in H2 at Room Temperature

Pt catalyst supported on carbon nano-tube (CNT) was extremely active for the selective oxidation of CO in H₂ at room temperature, which was remarked contrast to the Pt supported on an active carbon (Vulcan carbon) and a graphite powder. Complete oxidation of CO was attained on a 5 wt.% Pt/CNT catalyst (0.8 g) at ca. 40 °C when the O₂/CO ratio in a flow of H₂ (20 mL/min) + CO (3.0 mL/min) + O₂ + N₂ was adjusted to be larger than 0.75 at the total flow rate of 100 mL/min. Specific activity of the Pt/CNT catalyst was explained by efficient provision of reactant molecules diffusing on CNT surface to Pt particles.