Studies of the cathodic adsorption of hydrogen and the anodic formation of oxide on platinum in perchloric acid solutions using modulated specular reflectance spectroscopy

Abstract

The changes in reflectivity of a platinum electrode in molar perchloric acid accompanying the formation of a layer of oxide or of adsorbed hydrogen were investigated in the wavelength range 200–600 nm using modulated specular reflectance spectroscopy. Two correlation techniques, phase sensitive detection or signal averaging, were used to achieve a high sensitivity (± 2 × 10^–6). The origin of the reflectivity changes is discussed and it is shown that a simple three-phase model accounts for most of the effects. Two types of adsorbed hydrogen were distinguishable and the implications of the special optical properties of the more strongly bound species are discussed.