Kinetics of the Hydrogen Electrode Reaction on Platinum in Alkaline Solutions at Elevated Temperatures

Abstract

The kinetics of the hydrogen electrode reaction on a platinized nickel electrode in alkaline solutions over a wide temperature range from ambient up to 220oC have been investigated employing a controlled hydrodynamic cell. Due to the reversible nature of this reaction, the generalized Butler-Volmer equation was used in optimization upon the polarization data, so as to account for kinetic, thermodynamic, and mass transfer effects. The extracted model parameters are compared with those for other forms of platinum electrode, and platinized nickel shows excellent electrocatalytic activity as demonstrated by the exchange current density. The extracted apparent transfer coefficients for hydrogen evolution and hydrogen oxidation are temperature-dependent, while the apparent Tafel slope of the hydrogen evolution reaction is temperature-independent (approximately 120mV/dec), which is most probably due to two parallel reactions occurring at the interface with different rates and activation energies. An Arrhenius analysis yields an activation energy of 17.3 kJ/mole for the hydrogen electrode reaction on platinized nickel in alkaline solution.