Estimation of Exchange Current Density for the Hydrogen Evolution Reaction of Titanium in Sulfuric Acid Solution

Experimentally obtained polarization curve for the hydrogen evolution reaction on titanium in a 0.5 mol dm(-3) sulfuric acid solution was studied using curve techniques in the differential polarization method (DPM). The values of exchange current density (i(0)) were estimated to i(0) = 10(-2.6) similar to 10(-3.1) mA cm(-2) by the Tafel extrapolation method (TEM) and to i(0) = 10(-3) mA cm(-2) by the DPM, respectively. In addition, the DPM showed that the cathodic transfer coefficient was ca. 0.3. From viewpoints of easy and more accurate estimation, it was shown that the DPM has two advantages: (1) proper readings of the Tafel slope and (2) accurate elimination of undesired physical factors such as oxide film and solution resistance.