Electrochemical Characteristics of Air Electrode with Fe Phthalocyanine for Metal-Air Batteries

In order to fabricate the practical air electrode, the catalytic effects of iron-phthalocyanine (FePc) and FePc polymer (poly-FePc) were studied. Four methods were used to support FePc or poly-FePc on carbon; (1) Mixing, (2) Impregnating, (3) Evaporating and (4) Direct synthesizing (to synthesize poly-FePc on carbon). The polarization of electrodes became smaller in the order of no catalyst ≫ FePc (method 1) ≫ FePc (method 3) ≫ FePc (method 2) ≫ poly-FePc (method 2) ≫ poly-FePc (method 4). The electrode by method 4 (poly-FePc) kept ca.-0.2 V during 10 mA/cm² discharge for 230 hr, though the electrode by method 2 (poly-FePc or FePc) showed ca. 0.1 V drop during discharge. Open type Al-air cells were fabricated to examine the practical performance of the air electrodes. The cell with air electrode by method 4 (poly-FePc) showed higher voltage, compared with the cell with FePc electrode. The cell capacity was limited by formation of Al(OH)3 layer on Al electrode. From these results, the method 4 was found to be the best way to fabricate practical air electrode.