Kinetics of the Hydrogen Evolution Reaction on Mild Steel and Nickel Cathodes in Concentrated Sodium Hydroxide Solutions

• Published in: Journal of the Electrochemical Society 1982-11, Vol.129 (11), p.2481-2487
• Main Authors: Brown, Alan P., Krumpelt, M., Loutfy, R. O., Yao, N. P.
• Format: Article
• Language: English
• ISSN: 0013-4651; 1945-7111
• DOI: 10.1149/1.2123588

Data are reported on the kinetics of the hydrogen evolution reaction on mild steel and Ni cathodes in sodium hydroxide electrolytes from 4 to 50 wt.-% (1-26 m) for temp. of 288-358K. Measurements were made for both smooth and roughened electrode surfaces up to current densities of approx 0.3 A/cm exp 2 . Tafel plots for the Ni cathodes are linear over the whole current density range studied. The transfer coefficient, beta , has an average value of 0.54 and is unaffected by varying either the caustic concentration, the temp. or the surface roughness of the electrode. With the mild steel cathodes, the Tafel plots show two linear regions with the inflection point occurring at eta = 0.140 to 0.225 V. In the lower overpotential region, beta increases from approx 0.5 to at least 1.4 with increasing caustic concentration and increasing temp. The ability of the caustic concentration or the temp. to affect the reaction mechanism is amplified by roughening the electrode surface. For the linear regions in the Tafel plots at high overpotentials, the slopes are almost invariant to changes in the caustic concentration, the temp. or the surface roughness. The transition between the two Tafel regions appears to be caused by a change in the electrode surface resulting from the reduction of a surface oxide, possibly FeOH. The dependence of the inflection point potential on the experimental variables is analyzed in terms of this potential being equivalent to the equilibrium potential of the inferred surface redox reaction. 33 ref.--AA