ON THE FORMATION OF "Ag2O3" ON SILVER ELECTRODES

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Abstract
"Ag2O3" was examined electrochemically in eutectic KOH−H2O at −40 °C by coulombic measurements of quantities formed, open circuit potential decays, variation of potential as a function of anodic current density, and temperature coefficients of decomposition rates. It can be formed directly from Ag2O on Ag at current density (c.d.) > 15 μA/cm2, with a maximum thickness during the first oxidation cycle (25 layers, assuming a surface roughness factor of one) occurring at 65 μA/cm2. Potential decay (−∂E/∂ log t ≡ b) curves have protracted linear regions where 0.045 < b < 0.078, sometimes higher. One-tenth of a layer of adsorbed species superimposed on the higher oxide exists on the surface during O2 evolution. Reduction curves show a minimum in the potential decay of the higher oxide preceding the formation of Ag2O. The "Ag2O3" decomposes in approximately 1 h at −40 °C to either AgO or Ag2O. The activation energy for its thermal decomposition is 12.0 ± 2.0 kcal/mole. Under most experimental conditions studied the results indicated that the material is not true Ag2O3 but it is probably better described as Ag2O[O] where [O] is trapped oxygen.The evidence does point to the probable existence of a thin layer, which may be true Ag2O3, on the surface in a steady state which is maintained at high anodic current density ( > 100 μA/cm2 at −40°).

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