Enhancement of hydrogen evolution reaction on platinum cathode by proton carriers

The catalytic effect of aniline and benzylamine has been investigated for hydrogen evolution reaction on platinum electrode in sulfuric acid aqueous solution using voltammetric methods and electrochemical impedance spectroscopy. Kinetic parameters which characterize the hydrogen evolution reaction (cathodic transfer coefficient, exchange current density) have been determined using Tafel plots. It has been found that the addition of amines leads to an increase of the exchange current density, explained by an increased concentration of protons available at the interface. The catalytic effect of benzylamine and aniline is strongly correlated to their molecular parameters, such as dipole moment and molecular surface coverage. Also, apparent activation energies for hydrogen evolution reaction from solutions with and without addition of aromatic amines have been calculated. Electrochemical impedance spectroscopy results confirm an overall enhancement of hydrogen evolution in the presence of amines, as indicated by the lower values of charge transfer and adsorption resistances and by the decrease of characteristic time constants.