PREPARATION AND CHARACTERIZATION OF THIN-FILMS OF LANIO3 FOR ANODE APPLICATION IN ALKALINE WATER ELECTROLYSIS

LaNiO3 electrodes were prepared, in the form of thin films on platinum by the methods of spray pyrolysis and sequential coating of mixed met al nitrate solutions followed by thermal decomposition. The films were adherent and of p-type semiconducting. Cyclic voltammetric studies in dicated the formation of a quasireversible surface redox couple, Ni(II I)/Ni(II), on these films before the onset of oxygen evolution in 1 m KOH. The anodic Tafel slopes were approximately 40 and approximately 6 5 mV decade-1, on the sprayed LaNiO3 film and on the film obtained by a layer method, respectively. The reaction order with respect to OH- w as found to be 2.2 on the sprayed oxide film and 1.2 on the layer film . The sprayed oxide film was found to be electrocatalytically more act ive. It is suggested that the oxygen evolution reaction proceeds on bo th the film electrodes via the formation of the physisorbed H2O2 as an intermediate in the rate determining step.