Silver hydrogen overvoltage

A. Nidola and R. Schira. Deactivation of Low Hydrogen Overvoltage Cathodes in Chlor-Alkali Membrane Cell Technology by Metallic Impurities, In M.M. Silver and E.M. Spore (eds), Advatutes in the Chlor-Alkali and Chlorate Industry, The Electrochemical Society Inc., Princeton, NJ (1984), p. 206. 

The second type of cell is a mercury pool type. A mercury cathode is particularly useful for separating easily reduced elements as a preliminary step in an analysis. l or example, copper, nickel, cobalt, silver, and cadmium are readily separated from ions such as aluminum, titanium, the alkali metals, and phosphates. The precipitated elements dissolve in the mercury little hydrogen evolution occurs even at high applied potentials because of large overvoltage effects. A coulomet-ric cell such as that shown in Figure 24-5b is also useful for coulometric determination of metal ions and certain types of organic compounds as well. 

The reduction of molecular oxygen that is supplied either directly from containers or in a diluted form as air constitutes the reaction at the cathode in fuel cells. The use of air is preferable for economic reasons. Platinum metals and alloys of platinum metals are electrocatalysts for acid and alkaline electrolytes. Silver, silver alloys, nickel, carbon, and intermetallic compounds represent less expensive electrocatalysts for the oxygen electrode in alkaline solutions. In contrast to the hydrogen electrode, the overvoltage of the oxygen electrode is large at temperatures below 100 °C when a reasonable current is drawn. 

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