Electrochemical reactions temperature sensitivity

It has to be kept in mind that usually the temperature influence is less important, since large temperature gradients inside the fuel cell are normally avoided, for several reasons. First, a large temperature gradient imposes thermal stress on the respective materials and is a source of accelerated degradation or failure. Second, the electrochemical reaction is sensitive to temperature. An increase in temperature leads to an increase in current density. This in turn would amplify a nonideal current distribution, leading to an increase in losses connected with cross-currents. 

What are ways oul of this extreme sensitivity to impurities in electrode kinetics for most electrochemical reactions One way to reduce the effects of trace impurities from the solution in electrode kinetics is to use a liquid electrode because such electrodes can be made to form drops, the lifetime of which is small, so that the impurities from the solution don t have time to adsorb on the drops before they break off from the elechxxle. The electrode material then has to be mercury (the only metal that is liquid at room temperatures), so this approach is limited because mercury is a poor catalyst and one wishes particularly to work with electrode materials that catalyze electrode reactions well.27... 

High-temperature stabilized NO-, zirconia potentiometric sensors are also being utilized [187], The electrochemical reactions on zirconia devices take place at the triple-phase boundary, that is, the junction between the electrode, electrolyte, and gas [186], It has been reported that sensors composed of a W03 electrode, yttria-stabilized zirconia electrolyte, and Pt-loaded zeolite filters demonstrate high sensitivity toward NO,, and are free from interferences from CO, propane, and ammonia, and are subject to minimal interferences from humidity and oxygen, at levels typically present in combustion environments [188], In this sensor, a steady-state potential arises when the oxidation-reduction reaction [186,188]... 

In general, the electrochemical reactions taking place in a fuel cell assembly are exothermic. However, the catalyst employed in these reactions is normally sensitive to heat. To perform optimally, fuel cells should be maintained at a certain temperature that is nearly uniform across each cell in the stack. For example, at high temperatures, the catalyst may be destroyed, while at low temperatures, ice may form within the fuel cell assembly. Thus, to accommodate such temperature requirements, heat transfer compositions are needed. 

In fact, to is very sensitive to electrode surface condition and it is temperature-dependent as indicated by eq. (3.8). Thus, one can generalize the Arrhenius equation, eq. (3.2), for a series of electrochemical reactions as follows [47]... 

Cold electronic emission should not be confused with the electrochemical charge transfer process, where the equienergy state acceptor levels have to be present in the solution. To distinguish both mechanisms, temperature measurements are necessary. Electrochemical reactions obey Boltzmann statistics and are sensitive to temperature, in contrast to cold electron emission. 

---