The methanol oxidation activity of platinum-ruthenium nanoparticles on carbon supports and sputter-deposited films was investigated as a function of the surface composition. A technique combining the copper under-potential deposition and copper stripping was used to measure the surface platinum-ruthenium composition. The measurements showed that the surface composition was not always the same as the bulk composition even though an X-ray diffraction analysis showed that the platinum-ruthenium formed a solid-solution. Liner sweep voltammetry was used to measure the methanol oxidation activity in a 0.5 mol/L sulfuric acid solution containing 1.0 mol/L methanol at 308 K. The result from this electrochemical analysis showed that the methanol oxidation activity correlated with the surface platinum-ruthenium composition. The optimum surface composition was different between the nanoparticles and the films. The value for the nanoparticles was around 50 at% ruthenium, while for the films that was around 25 at% ruthenium.
A simple and useful technique for preparing an oxidation-resistant film on a Pb electrode is reported herein. A Pb electrode was dipped into a mixed solution containing 1% ascorbic acid and 5% boric acid at 40°C and then air-dried. The Pb electrode was coated with a film on its surface to protect it from oxidation. After three months, the oxide layers on the Pb plate were analyzed by treatment with pure ascorbic acid or boric acid. An oxidized layer was not observed on the plate treated with the mixed solution of ascorbic acid and boric acid; this was confirmed using an electron probe micro analyzer (EPMA). To further analyze the effect of co-absorption, the interaction between ascorbic acid and boric acid in solution was evaluated using a UV-visible spectrometer, and mixed solid samples were analyzed using FT-IR spectrometry.
Neutron radiography is a useful tool for the visualization of the water distribution in fuel cells. In this study, we prepared a high-spatial-resolution neutron imaging system and a small-sized fuel cell, and we observed the through-plane water distribution in the fuel cell after operation. Fuel cell operations were carried out while varying the gas flow rate in the constant-current mode. Under low-flow rate conditions, the voltage decreased as the operation time increased, dropping below 0.2 V after 7.5 min. A neutron image shows that water distribution was observed around the membrane electrode assembly (MEA) at the beginning of the operation, and it expanded over time to the gas diffusion layer (GDL) and the channel on the cathode side. The water thickness peak was located at the cathode-side GDL. Fuel cell operation was more stable under high-flow rate conditions than under low-flow rate conditions. Neutron imaging results suggest that stable fuel cell operation can be attributed to water discharge due to expulsion by the gas flow.