ELECTRODE KINETIC-PARAMETERS FOR THE HYDROGEN EVOLUTION REACTION ON PD IN ACID-MEDIUM - INFLUENCE OF THE ELECTRODE ACTIVATION

The hydrogen evolution reaction (h.e.r.) on the activated Pd electrode was studied. It was observed that its electrocatalytic performance changed with the derivatization time. The lowest overvoltage for the h.e.r. is obtained on Pd electromodified during 90 min. The sensitivity of the electrodes to impurity effects during the h.e.r. decreases on modified electrodes. The exchange current density of Pd decreases remarkably when Hg2+, Cd2+ or Pb2+ are present in the electrolysis electrolyte. Accordingly, Pd is very sensitive to these impurities. In contrast, modified Pd surfaces with SiW12O404 (Pd90SiW12) leads to better resistance to the impurities effect. The h.e.r. mechanism on Pd and Pd90SiW12 was studied between 298 and 358 K. The influence of the electrode surface activation on the kinetic parameters such as exchange current density and heat of activation of the constituent steps of the h.e.r. was deduced. The effect of the electrode surface activation on the variation of the overvoltage η and the Tafel slope with the temperature was also studied. It was shown that the temperature-dependence of η and the temperature-independence of b are confirmed experimentally if the electrochemical barrier symmetry factor (α) is taken as the temperature-independence. The activation of the electrode surface has no effect on this behaviour. © 1990.