I. Characterization of the Anodically Formed Oxide Film on Platinum Electrodes. II. Development of Electrochemical Instrumentation

Citation

Lauer, George (1967) I. Characterization of the Anodically Formed Oxide Film on Platinum Electrodes. II. Development of Electrochemical Instrumentation. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/9hyg-5140. https://resolver.caltech.edu/CaltechETD:etd-09262002-120406

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. The oxygen containing film formed at anodically polarized platinum electrodes in oxyacid solutions has been characterized. By making use of a thin layer electrode it is shown that the film is composed of Pt(II) and Pt(IV) oxides. This was proven by oxidizing the electrodes, and then stripping the oxides with acidic chloride solution and then analyzing, coulometrically, the platinum chlorides in solution. It is shown that the discrepancy between anodic charge passed during oxidation and the cathodic charge passed during reduction is due to Pt(IV) oxide which is not reducible at potentials anodic of the hydrogen evolution reaction. The oxides decompose slowly in formal sulfuric acid to form hydrogen peroxide and platinum; elevated temperatures accelerate the decomposition. A correlation is drawn between the presence of Pt(IV) on the surface of the electrode and "activation" of the electrode. It is concluded that the cause of activation is irreducible oxide. A standard electrode free of oxides can be obtained by immersion in 1 F H2SO4 at 100[degrees] C. It is proposed that such pretreatment is an excellent point of departure for further investigations with platinum electrodes. It is shown that ozone is evolved in sulfuric and perchloric acids at potentials more positive than 1.3 volts with respect to the saturated calomel electrode. The evolved ozone is reduced at 1.1 volts. In the second portion the use of operational amplifiers in electrochemical control and measurement instrumentation is discussed, and the simplified theory is presented. The design and construction of a multi-purpose electrochemical control instrument is discussed and a complete set of construction instructions is given. The last section considers the use of a small general purpose digital computer as an on-line digital data acquisition instrument. The interfacing and the logical circuitry required to perform electrochemical experiments with such a computer are described.

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