Electrochemical Properties of Electrode Coatings Containing Highly Oxidatively Active Platinum Oxides

Abstract

By time-programmed anodic and cathodic polarization (galvanostatic conditions and undivided cell) chemically stable coatings of hydrated higher valency platinum oxides were deposited from a 10% aqueous solution of alkali hydroxide saturated with PtO2 on platinum, nickel, titanium, iron and glassy-carbon electrode supports. Their voltammograms yield anodic and cathodic peaks over the whole pH region (0.15 to 13.20). The peaks corresponding to the transformation of higher valency platinum oxides are developed at more positive values (cathodic peaks between +0.57 and -0.35 V, and anodic peaks from +0.88 to -0.23 V vs SCE). The peaks corresponding to the transformations of PtO2 are located in a more negative region. Upon adding toluene or its derivatives their electrocatalytic oxidation over the whole pH region is intensified by increasing the temperature to 80 °C. The preparative coatings of hydrated platinum oxides prepared by the same technique on platinum grids were only deposited on a part of the electrode surface. The preparative electrolytic oxidation of toluene on these coatings leads only to low material yields: in 0.5 M H2SO4 it gives 4% benzaldehyde and in 0.25 M NaOH even less, i.e. 3%. The linear dependence of the increase of peak currents in voltammograms of coatings plotted as a function of the cathodic polarization potential (applied in the preceding preparation in strongly acidic media) points to a liberation of alkali metal cations intercalated in the coating of hydrated higher valency platinum oxides during their deposition.