The Mechanism of Oxygen Reduction at Platinum in Alkaline Solutions with Special Reference to H[sub 2]O[sub 2]

A rotating disk electrode with a concentric ring has been used to determine the role of hydrogen peroxide in the reduction of oxygen at platinum electrodes in alkaline solution. Oxygen reduction proceeds along two parallel reaction paths with comparable rates. In one of the paths, hydrogen peroxide is a reaction intermediate which is partially reduced to water. In the other, oxygen reduces to water without hydrogen peroxide as an intermediate. In the path with hydrogen peroxide intermediate, the first part of the probable sequence of reaction steps is shown to be The peroxide anion is thereafter reduced to water in a path which does not involve an electron transfer before or in the rate‐controlling step. Possible paths for oxygen reduction to water without peroxide intermediates are discussed in the light of already proposed mechanisms for the reduction at prereduced and preoxidized electrodes.