Nickel, Silver, and Carbon in Alkaline Electrolytes

Dissolution of Nickel, Silver, and Carbon in Alkaline Electrolytes 

The corrosion of nickel in alkaline solutions is small [2,22,23] in the potential region between the two parallel lines representing the equilibrium of reaction 6 and 7 respectively in Fig. 83. This is the potential range of interest for the operation of fuel cells. Studies [23] of the dissolution of Ni(OH)2 in NaOH up to 15 M suggest an upper limit of the 

Silver is stable in alkaline solutions in the potential range of interest since the formation of Ag2 0, which is soluble, occurs at more anodic potentials. 

The diagram for carbon in Fig. 83 displays a very small domain of stability. It is thermodynamically possible for carbons to be easily oxidized to carbon dioxide, carbonic acid, and carbonates. Reduction of carbon may lead to the formation of methane, methyl alcohol and other organic substances. However, the energetically possible reactions are strongly irreversible [2] and do not occur under normal conditions of pressure and temperature. Schmidt [24] reported a corrosive destruction of carbon electrodes when a critical potential was exceeded during the reduction of O2. The carbon electrodes were not impregnated with metallic electrocatalysts. The critical potential depended upon the extent to which an oxygen layer was present (compare section 5 in chapter VIII). 

— Atlas of Electrochemical Equilibria in Aqueous Solutions. Oxford Pergamon 

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