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Substoichiometric titanium oxide (Ti4O7)-supported Pt catalysts were prepared and their electrochemical properties, particularly the effects of high-potential conditions on the activity and stability of Pt/Ti4O7 catalysts, were compared to those of Pt/C catalyst. Polarization measurements using membrane electrode assemblies revealed that the Pt/Ti4O7 cathode shows a similar activity for the oxygen reduction reaction as Pt/C catalyst at 80°C. A high-potential holding test (1 h holding at 1.0-1.5 V vs anode) demonstrated that the Pt/Ti4O7 catalyst is quite stable against high potential up to 1.5 V. A single cell using a Pt/Ti4O7 cathode was operated at 80°C, and voltage stability for >350 h with H2/O2 was also demonstrated. [ABSTRACT FROM AUTHOR]

Abstract: To measure local phenomena in a PEMFC during a transitional state induced by changing of the feeding gas, a segmented cell was fabricated and the local current and local potential distribution were measured under open-circuit conditions. The anode or cathode was divided into 97 segments of 1.5mm each. A change in the anode gas from nitrogen or oxygen to hydrogen induced momentary internal currents among the segments. The potential distribution in the electrolyte was observed simultaneously using three quasi-reference electrodes located locally. The results supported the reverse-current decay mechanism, which is known to be a mechanism of cathode degradation. Furthermore, internal currents were observed when the cathode gas was changed from nitrogen to oxygen. While the cathode was not subjected to a harmful potential, a large potential distribution was induced in the anode. [Copyright &y& Elsevier]

Highlights: [•] WE examined the electrochemical behaviors of Co octaethylporphyrin (Co-OEP) on HOPG. [•] Co-OEP exhibits reversible voltammograms at high potentials on HOPG in sulfuric acid. [•] Some anions (halides and ClO4 −) affect the redox behaviors. [•] The high potential can be explained by the effect of ClO4 −. [•] Halides decreased CO oxidation by the Co porphyrin, while ClO4 − did not. [ABSTRACT FROM AUTHOR]

Abstract: The switchable generation of hydrogen from a hydrazine solution was achieved with an electrochemical cell that has a cobalt anode and a platinum cathode. The H2 generator is based on the combination of hydrazine electro-oxidation on cobalt anode and H2O electro-reduction on platinum cathode. The rate of H2 generation was regulated by switching with no power supply. Slight electricity was generated from this cell along with H2. This cell uses selective anode and cathode catalysts, and hence a membraneless (one-compartment) structure could be realized for the regulation of H2 generation. [Copyright &y& Elsevier]

Abstract: We found that a water-soluble cobalt tetraphenylporphyrin tetrasulfonic acid catalyzes the reduction of redox mediators (quinones and indigo carmine) by CO. The reduction was analyzed by constant-potential amperometry, UV-spectroscopy, and gas chromatography. The rate of this reaction was quantitatively determined by monitoring the reduced forms of these compounds by amperometry. The reduction rate significantly depended on the redox potentials of these compounds. Since the reduced forms of indigo carmine and quinones can act as a good fuel for fuel cells, this reaction can be regarded as the conversion of the fuel from CO to other redox active species. [Copyright &y& Elsevier]

In order to survey new CO-tolerant anode for the PEFC application, the addition of TaOx and NbOx to the Pt catalyst was examined in the electrochemical oxidation of CO in a sulfuric acid solution. Voltammetric peak potentials for the oxidation of CO pre-adsorbed on the Pt surface shifted to lower potentials by these additives, indicating an enhancement of electro-catalysis of Pt for the CO oxidation. Both oxides of Ta or Nb also bring about an inhibition of the CO adsorption rate onto the Pt surface. Concerted effect of these oxides with Ru is discussed for the CO oxidation over the PtRu-TaOx and the PtRu-NbOx anodes. [Copyright &y& Elsevier]