Hiroyasu Takenaka

Water Uptake of Perfluorosulfonic Acid Membranes from Liquid Water and Water Vapor

The water uptake of several perfluorosulfonic acid membranes from liquid water over the temperature range 25 to 130 C and from water vapor at 80 C was determined. For water uptake from liquid water, the water uptake depended on the immersion temperature, the ion exchange capacity of the membrane, and the pretreatment of the membrane. The effects of pretreatment were not significant at immersion temperatures higher than 100 to 110 C. For water uptake from water vapor at 80 C, the sorption isotherms were similar in shape of those reported by previous investigators for 18.5 to 30 C, although the water uptake at 80 C was less than that reported for the lower temperatures. The water uptake from water vapor of some membranes that have been found to give relatively good performance when used in polymer electrolyte fuel cells was higher then that observed with, e.g., Nafion[reg sign] 117.

Gas Permeation Properties of Solid Polymer Electrolyte (SPE) Membranes

Gas permeation properties for Nafion membranes and their composites were investigated under variou conditions. The permeability coefficients of Nafion depended greatly on the water content, the cation form, an the ion-exchange capacity. The gas permeation rate through a same sample varied with temperature, pressure, and membrane thickness. The permeability of hydrogen was about twice as great as that of oxygen. The electrocatalyst plated on the membrane did not serve as a barrier for gas permeation, but the structure of the catalyst layer played an important role in gas permeation during water electrolysis.

Iridium Oxide/Platinum Electrocatalysts for Unitized Regenerative Polymer Electrolyte Fuel Cells

To improve the water electrolysis performance of unitized regenerative fuel cells, ultrafine powder was synthesized from colloidal precursors, and an active electrode for oxygen evolution and reduction was prepared by mixing the powder and Pt black. Analysis showed that the surface area of the synthesized was higher than that of high‐surface‐area Pt black. During fuel cell operation, increased the overpotential slightly; however during water electrolysis, the mixed electrocatalyst had a considerably higher activity for oxygen evolution. The addition of only a small amount of to the oxygen electrode was sufficient for the unitized regenerative fuel cell.

IrO2-deposited Pt electrocatalysts for unitized regenerative polymer electrolyte fuel cells

An IrO2/Pt electrocatalyst for the polymer electrolyte-type unitized regenerative fuel cell (URFC) was prepared by deposition of iridium oxide (IrO2) particles on Pt black via a colloidal iridium hydroxide hydrate precursor, and URFC performance was examined. After the iridium hydroxide hydrate deposited Pt was calcined at 400 °C in air for 1 h, rutile-structure IrO2 particles (20–50 nm dia.) were formed on Pt particle clusters. TEM and pore volume distribution analysis revealed that the microstructure of the deposited IrO2/Pt catalyst was different from the mixed IrO2/Pt catalyst. The cell using the deposited IrO2/Pt (20 at % Ir) catalyst showed similar fuel cell performance with the mixed IrO2/Pt electrode of higher Pt content (10 at % Ir) while maintaining water electrolysis performance. Consequently, 51% round-trip energy conversion efficiency at a current density of 300 mA cm−2 was attained.

Catalytic activity of platinum after exchange with surface active functional groups of carbon blacks

The deposition of platinum on various carbon blacks has been carried out by forming active functional groups on the surface of the carbon support, and exchanging these active groups with different platinum complexes. Using H2PtCl6 solution, an aggregation rather than an exchange takes place. In this case, the anionic platinum complexes [PtCI6]2– involved have a tendency to form a coagulated platinum cluster after the reduction process. However, using ammonium platinum chloride, an exchange between the cationic platinum complexes and surface functional groups takes place. The exchange process involving the divalent platinum complex, [Pt(NH3)4]2+, is much faster than the one where the tetravalent platinum complex [Pt(NH3)6]4+, is involved. Transmission electron migrograph (TEM) photographs have shown that when using Pt(NH3)4Cl2 solution for the exchange, platinum particles are extremely small (0.75–1.7 nm) and highly dispersed on the surface of the carbon black. A comparison of the catalytic activities of platinum supported on various carbon blacks was also carried out. The catalytic activity mainly depends on the particle size rather than the loading amount of the catalyst.

New process for loading highly active platinum on carbon black surface for application in polymer electrolyte fuel cell

The deposition of platinum on various carbon blacks was carried out by forming active functional groups on the surface of the carbon support, and exchanging these active groups with different platinum complexes. Using H2PtCl6 solution, an impregnation rather than an exchange takes place. However, using divalent platinum complexes [Pt(NH3)4]2+, a fast exchange takes place which leads to extremely small platinum particles highly dispersed on the surface of carbon black. A comparison of the catalytic activities of platinum supported on various carbon blacks was also carried out. The performances of Pefc (Polymer Electrolyte Fuel Cell) based on the process of the ion exchange are reported.

Solid polymer electrolyte CO2 reduction

Abstract Solid polymer electrolyte was applied to CO 2 reduction. A zero-gap system with an anion exchange membrane and a porous PTFE sheet deposited solid electrolyte, and a water supply system from the anodic side by back-diffusion through the membrane were effective in the reaction.

Effects of Surface Roughening of Nafion® on Electrode Plating, Mechanical Strength, and Cell Performances for SPE Water Electrolysis

The most suitable conditions for surface-roughening Nafion membranes used as solid polymer electrolytes (SPE) were examined for their effect on electrode plating, mechanical strength, and cell performance for water electrolysis

Effects of Bath Condition on Plating Rate of Electroless Ni Films Prepared by Reducing Agent Permeation Method

The effects of such bath conditions as reducing agent concentration, Ni salt concentration and plating temperature on the rate of electroless Ni plating by the reducing agent permeation method were examined.At the initial nucleus formation stage, it was supposed that the mutual diffusion of BH4- and Cl- through the membrane was the rate determining step and the initial nucleus formation rate was proportional to the 0.2 power of NaBH4 concentration and NiCl2 concentration. The activation energies of the diffusion coefficients of both anious were calculated to be 4.57kJ/mol.At the Ni growth stage, it was estimated that in addition to the nutual anion diffusion, Ni diffusion was also the rate determining step.The rate of Ni growth was proportional to the 0.3 power of the NaBH4 concentration and the 0.7 power of the NiCl2 concentration. The activation energy of the rate constant was calculated to be 3.90kJ/mol. The rate of Ni growth can be controlled by these kinetic parameters.