Electrodes electrolytes for

Semiaqueous or Nonaqueous Solutions. Although the measurement of pH in mixed solvents (e.g., water/organic solvent) is not recommended, for a solution containing more than 5% water, the classical definition of a pH measurement may still apply. In nonaqueous solution, only relative pH values can be obtained. Measurements taken in nonaqueous or partly aqueous solutions require the electrode to be frequently rehydrated (i.e soaked in water or an acidic buffer). Between measurements and after use with a nonaqueous solvent (which is immiscible with water), the electrode should first be rinsed with a solvent, which is miscible with water as well as the analyte solvent, then rinsed with water. Another potential problem with this type of medium is the risk of precipitation of the KC1 electrolyte in the junction between the reference electrode and the measuring solution. To minimize this problem, the reference electrolyte and the sample solution should be matched for mobility and solubility. For example, LiCl in ethanol or LiCl in acetic acid are often used as the reference electrode electrolyte for nonaqueous measurements. 

Fig. 9.5 Scheme of the three-phase boundary sites in an interface electrode—electrolyte for electrodes with different sizes of metal particles. Porous electrodes help to increase the density of three-phase boundary sites. Idea from Lopez-Gandara et al. (2009)... 

We usually assume a three-phase boundary of gas-electrode-electrolyte for the electrode reactions to take place. Therefore, the foregoing experimental results suggest that the electrocatalytic activity of platinum for the cerate will be much higher than that for the zirconate. The electrode reaction zone will not be restricted to the three-phase boundary, which is mathematically one... 

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See also in sourсe #XX -- [ ]

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