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) sul fate 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, res pectively, showed deficiency with Co(III) ions in the film structure. All f ilms exhibited substantial electrical conductivity (a) which was slightly d ependent on the type of the substrate. The roughness factor, RF, of electro des was determined by cyclic voltammetry. Spinel oxide films prepared at lo wer temperatures (300 degrees C) showed high surface area (RF similar to 70 0). The electrocatalytic properties were studied by different electrochemic al methods in alkaline solutions. The results of electrochemical measuremen ts in KOH indicated the formation of surface quasi-reversible redox couple, Co(IV)/Co(III), which is limited by a diffusion-controlled process. The ox ygen evolution potentials pointed out remarkable performance of Co3-xO4 (30 0 degrees C) and Li+ doped Co3-xO4 (500 degrees C) films. The reaction orde r with respect to [OH-] was found to be nearly 1.2. Durability testing of f ilms in 5 M KOH at 70 degrees C showed high long-term performance and struc ture stability of Li+ doped Co3-xO4 (500 degrees C) films. (C) 2000 Elsevie r Science I,td. All rights reserved.