Steady state experimental evaluation of a Novel raney-Ni/PTFE gas diffusion electrode in an alkaline fuel cell

Abstract

Steady state polarization measurements on specially prepared Raney-Ni/PTFE gas diffusion electrode impregnated with copper oxide were carried out. The long term performance of the electrode was also investigated in a half cell setup with 25% KOH solution. Pure hydrogen gas was fed to the half cell at a pressure of 1.4 bar. The electrolyte temperature was varied from 25℃ to 75℃. The better performance (less polarization) at higher current densities is attributed to the addition of copper to the electrode. Spherical Raney-catalyst grain model was applied to determine the kinetic parameters, exchange current density(i₀) and charge transfer coefficient for the electrode. The values found for the exchange current densities at various temperatures were 6.6x10⁻⁶ to 3.1x10⁻⁴ Acm⁻². Exchange current density followed an exponential relation with temperature. Apparent activation energy for the electrode was found to be 28kj/mol lower than that reported in the literature. The lower activation energy for hydrogen. Oxidation reaction implied higher electroactivity of the electrodes of this type. Long term performance tests showed that electrode overpotential greater than 50 mV cause rapid deactivation of the electrode. The apparent deactivation constants estimated for the electrode vcaried from 0.004 hr⁻¹ to 0.032 hr⁻¹. The rate of deactivation is more at higher temperatures.₀