Reversible Oxygen Electrodes

Abstract

The reversible oxygen electrode has been set up on anodized platinum in ultrapure sulfuric acid solutions. The essential conditions for establishing the reversible oxygen electrode are described. It is found that the variation of the electrode potential with partial pressure follows the theoretical expression. At other stable potentials exhibited by the platinum oxygen system the partial pressure effects give variations not consistent with any theoretical formula. Decay curves on open circuit have been measured and a dependence on the oxygen partial pressure has been observed. In ultrapure solutions the potential decays after several hours to a limiting value of 1.1v corresponding to the potential. When the solutions are impure the limit is lowered to about 0.84v which is the equilibrium potential of the hydrogen peroxide system. The gold‐oxygen system also exhibits a number of different oxide potentials, one of these is at 1.23v in normal acid solution. The apparent establishment of the reversible oxygen electrode potential on gold must be viewed with caution as the overpotential for the mixed reduction of gold oxide and oxygen can give rise to spurious Tafel lines. The oxygen partial pressure effect on gold electrodes does not follow the Nernst equation. It therefore appears that the reversible oxygen electrode is not set up on gold.