Membrane electrode assemblies based on porous silver electrodes for alkaline anion exchange membrane fuel cells

Porous silver membranes were investigated as potential substrates for alkaline fuel cell gas transport electrodes by both electrochemical half-cell measurements in aqueous KOH electrolyte and production of fuel cells utilising an anion-exchange polymer electrolyte. The silver membranes provide both electrocatalytic function, mechanical support and a means of current collection. The gas transport layers are cost effective compared to current gas transport media (∼3× more expensive) especially considering their greatly reduced thickness, and several hundred-fold superior electrical and thermal conductivity. Utilising Teflon-AF as a hydrophobisation agent allows production of very high performance cathodes, with platinum-free performance under oxygen at 25 °C of 248 mA cm−2 (0.70 V vs. RHE) and 575 mA cm−2 (0.60 V vs. RHE). Addition of a small amount of platinum (100 μg cm−2) increases the cathode performance to 1071 mA cm−2, and 1756 mA cm−2, respectively. An alkaline anion exchange membrane fuel cells constructed utilising these electrodes and an anion-exchange polymer electrolyte shows an open circuit potential of 1.05 V and a performance of 100 mA cm−2 at 0.6 V (60 mW cm−2).