Electrodes at Low Temperatures

The corrosion of electrodes in fuel cells leads to a decrease in performance with time. It may determine the life of the fuel cell. The rate of corrosion depends upon the electrode material, the electrolyte and the temperature. The presence of anions which form complexes with the respective electrocatalyst (for instance C for platinum metals) has to be avoided since complex formation tends to increase the rate of corrosion. In general, corrosion problems become more serious with increasing temperature. While the corrosion of electrocatalysts is discussed in this chapter, the degradation of electrode structures due to mechanical strain or to the disintegration of the bonding material is not dealt with. 

---

Recent preliminary measurements of the electrokinetics of simple redox reactions at electrodes at low temperatures (— 40 to — 120°C) have shown a decrease of the energy of activation with decreasing temperature, which may indicate the occurrence of nuclear tunnelling [77]. 

Interesting ternary chalcogenides have been prepared employing electrochemical methods via anodic dissolution of copper or silver electrodes at low temperatures. For example, the series of KCu - S4 (0 < x < 0.34) was prepared in an ethylenediamine solution of polysulfide K2S (x = 5, 6) electrolytes. Single crystal stmcture analysis confirmed the once ambiguous space group of these compounds and showed that the KCU7S4 phase which exhibits an unusual insulator-to-metal transition is non-stoichiometric. The stmcture... 

Mechanically stable faujasite-type films were grown hydrothermally on glassy carbon electrodes at low temperature.[92] The authors succeeded in demonstrating charge- and size-... 

Although ASTM tests use temperature to accelerate attack during exposures, temperature can also be used in combination with electrochemical techniques. One example of this is the determination of critical pitting temperatures (CPT) [76,37,32] for alloy development or selection, or both. An anodic potential is applied to an electrode at low temperature (room or below) in the solution of interest and the temperature slowly increases in order to determine the temperature at which initiation of localized corrosion occurs, as signified by an increase in the current above some criterion. Such a method allows a quantitative ranking of materials in terms of resistance to pitting. 

---