Characterization of spinel Co3O4 and Li-doped Co3O4 thin film electrocatalysts prepared by the sol-gel route

Spinel Co3O4 and Li-doped Co3O4 thin film electrocatalysts deposited on Pt and ITO/glass substrates were prepared by the sol-gel route from Co(II) sulfate precursor using dip-coating technique. Stoichiometry of undoped and Li+ doped films (up to 10 mol% of Li+) prepared at 300 and 500 degrees C, respectively, showed deficiency with Co(III) ions in the film structure. All films exhibited substantial electrical conductivity (a) which was slightly dependent on the type of the substrate. The roughness factor, RF, of electrodes was determined by cyclic voltammetry. Spinel oxide films prepared at lower temperatures (300 degrees C) showed high surface area (RF similar to 700). The electrocatalytic properties were studied by different electrochemical methods in alkaline solutions. The results of electrochemical measurements in KOH indicated the formation of surface quasi-reversible redox couple, Co(IV)/Co(III), which is limited by a diffusion-controlled process. The oxygen evolution potentials pointed out remarkable performance of Co3-xO4 (300 degrees C) and Li+ doped Co3-xO4 (500 degrees C) films. The reaction order with respect to [OH-] was found to be nearly 1.2. Durability testing of films in 5 M KOH at 70 degrees C showed high long-term performance and structure stability of Li+ doped Co3-xO4 (500 degrees C) films. (C) 2000 Elsevier Science I,td. All rights reserved.