Fuel cells hold promise as alternative power sources due to their ability to bypass Carnot efficiency limitations by directly converting chemical energy into electrical energy. However, the high costs of catalysts and membranes, as well as component durability issues, have barred widespread implementation. Alkaline fuel cells (AFCs) have gained increasing attention due to superior electrode kinetics in alkaline media, compared to acidic media, which enables the use of non-noble metal catalysts . However, analysis of individual electrodes within an operating fuel cell is typically hampered by the reliance on overall measures such as maximum power density and open circuit potential. Standard electrochemical analysis, such as RDE (ring disk electrode) experiments, commonly characterizes catalyst activity and stability under conditions which are very different from those found in an operating fuel cell (e.g., 0.1 M KOH vs. 1-7 M KOH).
Previously, we have developed a pH-flexible flowing electrolyte microfluidic fuel cell, which uses an external reference electrode to individually analyze cathode and anode performance. This microfluidic configuration combines the versatility of a traditional three electrode cell with the conditions found in an operating fuel cell. To date, typical analyses have mainly consisted of qualitative comparisons between electrodes as a function of operating conditions and/or catalyst type. These analyses compared inward or outward shifts for a given electrode and the onset of mass transport limits. Quantitative comparisons have been restricted to maximum power / current density and open circuit potential, which do not utilize the advantages of an external reference electrode.
Here, we present a method systematically analyzing the performance of individual electrodes within an operating fuel cell. This in-situ single electrode analysis enables detailed quantification of kinetic, ohmic, and mass transport losses as compared to a reference electrode. The effects of varying catalysts, reactant delivery, and electrolyte compositions are determined. These detailed measurements can be used to better understand the impact of local environments and electrode preparation techniques on the performance and durability of fuel cell systems.
 Brushett et al., Journal of the Electrochemical Society, 2009, 156, B565