LaFe CoO Thin-Film Oxygen Reduction Catalysts Prepared Using Spray Pyrolysis Without Conductive Additives

LaFe CoO thin films were prepared on fluorine-doped tin oxide conducting glass substrates by spray pyrolysis without any conductive additives and evaluated for their ability to catalyze the oxygen reduction reaction. Onset potential and current density were found to be comparable to platinum, and the resulting crystallite size was on the order of 20 nm. Coordination of the precursor metal ions by citrate was found not to be advantageous. Results from multiple scan linear sweep voltammetry suggest lattice oxide saturation during reduction of oxygen and lattice oxide depletion upon water oxidation. The color of the best-performing composition changes dramatically between 1.2 and -1.15 V versus saturated calomel electrode, so X-ray photoelectron spectra of the fully oxidized and reduced films were compared, demonstrating that cobalt in the film changes oxidation state. Performance of the films as a function of iron-to-cobalt ratio is consistent with what others have reported in the literature, indicating that spray pyrolysis is an efficient method to prepare and evaluate new catalytic materials.