The Effect of Metal Dissolution on the Rest Potential in the Palladium-Oxygen-Acid System

Abstract

The rest potential of palladium electrodes in oxygen‐saturated sulfuric acid solutions was studied as a function of pH and the partial pressure of oxygen. In the absence of anodic polarization, a rest potential of is obtained which is a mixed potential, and this system is referred to as a electrode. After anodic polarization but in the absence of peroxide, a rest potential of is obtained which is an equilibrium metal‐metal oxide potential, and this system is referred to as a electrode. With time, a electrode is transformed to a electrode because is unstable in acid solutions. In a certain potential region, Pd dissolves in acid solutions to form Pd⁺⁺ ions which greatly influence the rest potential. Evidence is presented which indicates that, of all the noble metals, possibly Pd is the only one for which the evolution of oxygen under anodic polarization proceeds through an oxide mechanism.