The amount of hydrogen and oxygen present on the surface of a metallic electrode

Abstract

In a pervious communication a study has been made of the potential changes which occur during the discharge of small quantities of electricity at metallic cathodes in an acid electrolyte. The electrode potential was, in general, more negative than the reversible hydrogen electrode, and it was found that over this range the potential change was a linear function of the quantity of electricity passed. This quantity was very small, 6 X 10 -7 coulombs per square centimetre causing a change of 100 millivolts in the electrode potential at a mercury surface. This linear relation was found on all the metals investigated, but the quantity varied with the nature and condition of the surface, being greater the rougher the surface. Experiments with amalgams, and platinised mercury surfaces showed that this quantity was, to a first approximation, accessible area of its surface. It was suggested that this change in potential may be regarded as due to the deposition of more hydrogen dipoles to the surface, or alternatively to a flux of electricity across the interface causing a further deformation of the hydrogen dipoles already present on the surface. Although the potential changes accompanying these additions to the surface have been studied, few measurements were made of the quantity of hydrogen initially present on the surface at the reversible hydrogen potential. It was considered probable that this was approximately a monatomic layer but it was of some interest to investigate this point.