Structural analysis of alkaline fuel cell electrodes and electrode materials

Abstract An attempt has been made to characterize gas diffusion electrodes and electrode materials used in alkaline fuel cells. A number of techniques such as intrusion porosimetry, surface area analysis, scanning (SEM) and transmission (TEM) electron microscopy in conjunction with X-ray energy spectroscopy (XES), have been used to determine the relation between structural parameters and electrochemical performance. Intrusion porosimetry was given special attention. Mercury intrusion curves were compared with the intrusion behavior obtained with 12 N KOH electrolyte. It became obvious that the electrode structure consists of two components: a primary (macro) structure providing the skeleton of the electrode and determining the mechanical strength, and the secondary (micro) structure ensuring gas transport. The electrochemical reactions proceed in the boundary between the macro and the microstructure near the outside of the carbon particles where the reactant gas, electrolyte, and electrocatalyst meet in a three zone interface.