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

Abstract

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 O2+e−⇄O2− O2−+H2O→HO2−+OH OH+e−⇄OH− 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.

Dual band electrodes in generator–collector mode: Simultaneous measurement of two species

“…[48][49][50] Other areas in which generator-collector systems have been successfully employed include detection of micromolar concentrations, 44 studies of triple phase boundaries, 42 and measurement of one species in the presence of other, interfering, species.…”

Oxygen-Containing Nanoclusters on the Surface of Pt-Electrodes and Oxygen Reduction Reaction in Alkaline Medium

“…It was experimentally demonstrated (for example, [34][35][36][37]) that quantity of HO 2 − ions detected on the ring depends on surface conditions of polycrystalline Pt-electrode. Preliminary anodic oxidation or cathodic reduction is accompanied by a change of ring/disk current ratio.…”

Principles and Materials Aspects of Direct Alkaline Alcohol Fuel Cells

“…Effects of different pH, electrolytes, temperature and pre-conditioning of electrodes on ORR have been investigated. The most accepted mechanism of ORR was first proposed by Damjanovic et al [40,41]. They suggested that the ORR proceeds along two parallel reaction paths with comparable rates.…”

“…The reaction is first order with respect to O 2 in solutions. It was found that the amount of H 2 O 2 formed is greater in alkaline than in acid media [40,44]. In alkaline solutions, about 80% of the reduction current is via the direct reduction and the remainder of the current goes to the formation of H 2 O 2 , which suggests a more complicated mechanism.…”