High-performance self-humidifying membrane electrode assembly prepared by simultaneously adding inorganic and organic hygroscopic materials to the anode catalyst layer

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A novel self-humidifying membrane electrode assembly (MEA) has been successfully prepared by adding both a hydrophilic organic polymer (polyvinyl alcohol, PVA) and an inorganic oxide (silica) to the anode catalyst layer. This MEA shows excellent self-humidification performance under low-humidity conditions. A sample containing 3 wt.% PVA and 3 wt.% silica in the anode catalyst layer achieves a current density as high as 1100 mA cm−2 at 0.6 V, and the highest peak power density is 780 mW cm−2, operating at 60 °C and 15% relative humidity for both anode and cathode. The sample also shows excellent stability at low-humidity: after 30 h of continuous operation under the same conditions, the current density decreases just slightly, from 1100 mA cm−2 to ca. 900 mA cm−2, whereas with MEAs to which only PVA or silica alone had been added, the current densities after 30 h is just 700 mA cm−2 and 800 mA cm−2, respectively. The improved self-humidification performance can be attributed to the synergistic effect of two hygroscopic materials in the anode catalyst layer.