Ohmic Correction to the Electrode Potential

Using a Luggin probe introduces an error into the measurement of potential due to the gap which exists between the Luggin tip and the electrode surface. Consider the diagram in Fig. 3.13. The electrode potential E is given by Eq. (1.14)  

The difficulty of measuring the gap between the Luggin and the electrode surface precludes the calculation of iR. Indirect methods have to be employed three of them are described below. 

FIGURE 3.14. Ohmic correction for hydrogen evolution, x — Raw data, = data corrected for ohmic drop. 

After assembling a laboratory cell before experimentation, it is first filled with 0.5 M sulfuric acid and polarization data for hydrogen evolution are determined for current densities Km 

TABLE 3.7. Polarization Data for the Hydrogen Evolution Method 

---