IrO 2 -RuO 2 , IrO 2 -Pt and IrO 2 -Ta 2 O 5 electrocatalysts were synthesized and characterized for the oxygen evolution in a Solid Polymer Electrolyte (SPE) electrolyzer. These mixtures were characterized by XRD and SEM. The anode catalyst powders were sprayed onto Nafion 117 membrane (catalyst coated membrane, CCM), using Pt catalyst at the cathode. The CCM procedure was extended to different in-house prepared catalyst formulations to evaluate if such a method could be applied to electrolyzers containing durable titanium backings. The catalyst loading at the anode was about 6 mg cm -2 , whereas 1 mg cm -2 Pt was used at the cathode. The electrochemical activity for water electrolysis was investigated in a single cell SPE electrolyzer at 80°C. It was found that the terminal voltage obtained with Ir-Ta oxide was slightly lower than that obtained with IrO 2 -Pt and IrO 2 -RuO 2 at low current density (lower than 0.15 A cm -2 ). At higher current density, the IrO 2 -Pt and IrO 2 -RuO 2 catalysts performed better than Ir-Ta oxide.

The adsorption and electrooxidation of CO on polycrystalline Ag at pH 13, 9.2, 7, and 0.3 have been studied by cyclic voltammetry and Fourier transform infrared spectroscopy (FTIRS). At the four pH values the cyclic voltammograms (CVs) showed the formation and electroreduction of underpotential (UP) Ag oxides, i.e., oxides formed at potentials lower than the equilibrium potential of the Ag/Ag2O couple. Two pairs of peaks of UP oxides appeared at pH 13 and 9.2, but only one pair at pH 7 and 0.3. At pH 13 and 9.2 the current density of the anodic peak of the UP oxide appearing at the more positive potential increased if the solution was saturated with CO, and its peak potential increased (pH 13) or remained the same (pH 9.2), indicating the electrooxidation of adsorbed CO. Both at pH 7 and 0.3 the anodic peak in the presence of CO appeared at potentials 0.2 V more negative than that in the corresponding base electrolyte. Only at pH 13 did the CO adsorbed on Ag remain adsorbed after eliminating the dissolved CO by N2 bubbling, indicating that CO was strongly adsorbed. The FTIR spectra showed, at the four pH values, a band at 1970−2000 cm-1 assigned to CO linearly adsorbed on Ag and, at neutral and alkaline pH, a band at 1860−1900 cm-1 assigned to CO adsorbed in a bridge position. At pH 9.2, 7 and 0.3 there appeared a band at 2048 (pH 9.2 and 7) or 2112 (pH 0.3) cm-1 whose frequency did not change with potential and whose intensity increased with increasing potential and which was therefore assigned to CO adsorbed on an UP Ag oxide.

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Gold bead electrodes were modified with submonolayers of 3-mercaptopropionic acid or 2-aminoethanethiol and further reacted with poly(amidoamine) (PAMAM) dendrimers (generation 4.0 and 3.5, respectively) to obtain films on which Prussian Blue (PB) was later absorbed to afford mixed and stable electrocatalytic layers. Experiments carried out with these novel materials not only showed an improved surface coverage of PB on the dendrimer modified electrodes as compared to PB modified gold electrodes prepared under acidic conditions, but also showed an increased stability at neutral pH values for one of the dendrimer containing substrates where the PB film on a bare gold electrode is simply not formed. The dendrimer modified electrodes were also tested as electrocatalytic substrates for the electroxidation of L(+)-ascorbic acid (AA), and it was found that their sensitivity as well as the corresponding detection limits were improved as compared to the voltammetric response of a Au-PB modified electrode. On the basis of UV-visible (UV-vis) spectroscopy and electrochemical experiments, it is suggested that the PB molecules are located within the dendritic structure of the surface attached PAMAM dendrimers.

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