Reverse Micelle Assisted Dispersion of Lanthanum Manganite on Carbon Support for Oxygen Reduction Cathode

It was tried to disperse LaMnO 3+δ oxide finely on carbon black support through a reverse micelle (RM) method using poly(oxyethylene) 5 nonylphenyl ether (surfactant), and cyclohexane (solvent). An RM dispersion containing a nanosized precursor of the oxide [RM (C)] was prepared by mixing an RM dispersion containing nitrates of constituent metals [RM (A)] with another dispersion containing N(CH 3 ) 4 OH. RM (C) was easily destabilized with the addition of ethanol to deposit the precursor, which was converted to hexagonal oxide (LaMnO 3.15 ) or orthorhombic oxide (LaMnO 3.00 ) by calcination in air or N 2 , respectively. Carbon black powder was mixed at various stages of these preparation procedures. Among the resulting carbon-supported oxide powders, the one for which the carbon black was suspended into RM (A) was found to give an outstanding cathodic activity: It allowed current density as high as 300 mA cm -2 at -80 mV (vs. Hg/HgO) in 8 M KOH at 60°C under air flow. Transmission electron microscope observation revealed that fine dispersion of the oxide particles in the carbon matrix is the origin of such high activity.