Experimental study and modeling of impedance of the her on porous Ni electrodes

The electrochemical activity towards the hydrogen evolution reaction of pressed powder electrodes (NiZn and NiAl) was studied in alkaline solutions after leaching out the more active element. These electrodes displayed porous character, and electrochemical impedance spectroscopy was used to characterize surface porosity. The influence of overpotential, temperature, poisons, electrode composition and electrolyte concentration was studied and distinction criteria between faradaic and geometrical effects were formulated. Digital simulations of impedance values in different pore geometries were also carried out. The kinetic parameters of hydrogen evolution were determined. The main factor influencing the electrode activity seems to be the real surface area.