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The details of the preparation and characterization of co-deposited Pt/WO3 electrodes are presented. X-ray, scanning, and transmission electron microscopic studies revealed that WO3 is amorphous and that -40 APt crystallites are uniformly dispersed in the deposit. The influence of the deposition conditions and the effect of the solution acidity on the activity of such electrodes for methanol oxidation have been studied. The results demonstrated that the Pt/WO3 electrodes are much more active and more resistant to poisoning than Pt or Pt/Ru alloy catalysts. The reaction mechanism was studied by various electrochemical and surface analysis techniques. A reaction scheme that involves successive stepwise dehydrogenation of methanol, formation/oxidation of hydrogen tungsten bronze, and oxidation of organic intermediates and CO at the Pt/WQ interface is proposed.

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The minimum potential for the evolution of oxygen on six oxides ( RuO2Li0.1Ni0.9O , Li0.3Co2.7O4 , IrO2 , PbO2 , and PtO2 ) in 5NKOH has been studied by potentiostatic steady‐state and galvanostatic charging experiments. The results show that there is an excellent correlation between the minimum potential for oxygen evolution on the first three oxides and their lower oxide/higher oxide couples ( RuO2/RuO4=1.387V ; Ni2O3/NiO2=1.43V ; Co2O3/CoO2=1.447V ) listed in Pourbaix diagrams. For IrO2 , there was good agreement between the lower oxide/higher oxide couple false(IrO2/IrO3=1.35Vfalse) determined in this work by galvanostatic charging. Galvanostatic charging on PbO2 and PtO2 indicates that oxygen evolution takes place at 1.76 and 1.71V, respectively. However, these two values do not correlate with their lower oxide/higher oxide couple values. It is therefore suggested that oxygen evolution on such oxides proceeds via the OH−/HO2− couple (1.77V), where the reaction intermediates are physisorbed. We also discuss the stability of the lower and higher oxides of the six metals considered from the point of view of the crystal field concept.

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Oxygen evolution studies were carried out on preanodized Teflon‐bonded Co3O4 and Li‐doped Co3O4 electrodes in KOH medium. The oxygen evolution performance was found to increase with increase in Li doping. The results suggest the Co3+ ions are the major active sites for oxygen evolution. Steady‐state current‐potential measurements gave a Tafel slope of ∼60 mV per decade on all the oxides. This Tafel parameter was confirmed by potentiostatic transient measurement. A mechanistic sequence for oxygen evolutionT+OH−→TOH+e TOH+OH−→TO−+H2OO/ \ TO−+M→TM+e O/\2TM→2T+2M+O2has been put forward where T is trivalent cobalt and M is divalent or trivalent cobalt. The proton abstraction step is rate determining. This is supported by experimental reaction order parameters. These studies enabled the development of an efficient oxygen evolution electrocatalyst. Teflon bonded, preanodized, 10 a/o Li‐doped CO3O4 electrode was found to be 1.52V vs. the dynamic hydrogen electrode (DHE) at a current density of 1A cm−2 in 5NKOH in 70°C. Laboratory durability tests carried out on these electrodes under practical conditions showed good stability of structure and performance for 5800 h.

Electrodeposition of cobalt in aqueous chloride solutions has been studied by means of cyclic voltammetry and potentiostatic current-time transient techniques on rotating nickel disk electrodes. The electrocrystallization of cobalt is via a three-dimensional progressive nucleation and crystal growth mechanism under interfacial electron transfer/mass transfer control. As the deposition proceeds, concentration polarization becomes increasingly important after the nickel disk electrode is nearly or fully covered by cobalt crystallites. However, as the bulk concentration of Co 2 § ions increases, the kinetics of the nucleation and crystal growth is increasingly dominated by interfacial electron transfer. It has also been found that in the electrodeposition process influenced by both interfacial/mass transfer p~ocesses, the electrode kinetics parameters can be obtained by analyzing the cathodic current responses of the reverse sweeps on the voltammetric curves. The measured Tafel slope of 29 mV and diffusion coefficient of 0.53 • l0 -9 cm 2 s -1 are in good agreement with the values reported in the literature.