Hyperpolarization of gas evolving electrodes—I. Aqueous electrolysis

✍ Scribed by James A. Leistra; Paul J. Sides

• Book ID: 103066643
• Publisher: Elsevier Science
• Year: 1987
• Tongue: English
• Weight: 580 KB
• Volume: 32
• Category: Article
• ISSN: 0013-4686
• DOI: 10.1016/0013-4686(87)85090-9

✦ Synopsis

Electrodes evolving oxygen and hydrogen in aqueous media were rotated at up to several thousand rpm in order to shear away gas bubbles and allow measurement of a voltage component, called hyperpolarization, due to masking of the electrode by gas bubbles. The difference in overpotential between rotated and non-rotated electrodes increased as a function of rotation rate at low rpm and then reached a plateau between one and three thousand rpm. Upon further rotation, the voltage difference increased again. The plateau was the hyperpolarization in the measurement, less then five mV at 0.1 A cm-', that corresponds to an effective surface coverage of less than 10%. The increase beyond the plateau marked the relief of the supersaturation of the electrolyte with product gas near the electrode. NOMENCLATURE superficial area of a gas-evolving electrode, cm2 area available for current flow on a gas evolving electrode, cm2 Tafel slope, V potential measured between the working electrode and a reference electrode of the same kind after current interruption, V average surface overpotential at the working electrode, V average gas concentration overpotential at the working electrode, V surface overpotential of the working electrode if no bubbles were present and theelectrode operated at the superficial current density, V hyperpolarization of the working electrode due to non-uniform current distribution associated with the presence of gas bubbles, V Superscripts h hyperpolarization r rotating s stationary