Potential of emersed electrodes in inactive gas

The relative work function and the relative electrode potential of electrodes in aqueous solutions and in inactive gases can be measured by a vibrating capacitor technique called Kelvin s method [Samec-Johnson-Doblhofer, 1992]. The Kelvin method estimates the difference in the work function between a test electrode and a Kelvin probe (KF) by measuring the applied voltage V at which the difference in the outer potential ij s- l KP between the test electrode and the Kelvin probe becomes zero (V = liJs - i Kp) as shown in Pig. 4—28. 

Since the difference in the outer potential ifs - kp equals the difference in the real potential-(ag(M/s Ao-a (KP))/c of electrons and hence the difference in the work function (d M/sA -d Kp)/e, Eqn. 4-39 can be obtained and represents the difference between the electrode potential. E of an immersed electrode (M/SA ) and the potential Ekf of the Kelvin probe (Fig. 4-28a)  

This equation applies also to the electrodes emersed from aqueous solution into inactive gas (Fig. 4-28 b) as shown in Eqn. 4-40, which gives the relationship between the electrode potential Em of an emersed electrode and the potential Ejcp of the Kelvin probe  

A linear relationship (straight line with unit slope) is observed in Fig. 4-29 between the electrode potential E measured by a conventional method and the electrode potential E-Ekp measured by the Kelvin method for equilibrium 

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