DEACTIVATION STUDIES ON THE POROUS NI-GAS DIFFUSION ELECTRODE IN H-2 O-2 ALKALINE FUEL-CELL/

Long term performance tests were carried out potentiostatically for th e Cu-impregnated Ni-gas diffusion electrode at Various temperatures. T o measure the deactivation with time, the voltage between the working electrode and the reference electrode was kept constant and the fall o f current density (i.e. the reaction rate) was monitored as a function of time. At almost every temperature there was a decay of activity. T he higher the temperature the faster the observed deactivation rate wa s. The deactivation model assumed a first order reactant-gas-concentra tion-independent deactivation. The spherical flooded grain model was u sed for the determination of the deactivation rate constants (k(d)s) a t different conditions. Deactivation is attributed to: (a) dissolution of promoter Cu and Ni, hence reducing the electronic contact; (b) for mation of Ni(OH)(2) which passivates the electrode; (c) the change in the hydrophobicity of PTFE; and (d) dissolution of atmospheric CO2 in the KOH, forming K2CO3. Copyright (C) 1996 International Association F or Hydrogen Energy.