The oxygen evolution on La0.5Ba0.5CoO3 : Passivation processes

Abstract

Earlier publications on the oxygen evolution of La0.5Ba0.5CoO3 have left a number of observations involving passivation effects of the electrode unexplained. Therefore, the electrode surface used was studied by means of X-ray powder diffraction and electron microscopy (with diffraction and elemental analysis). It could be concluded that the surface had partly been changed into (hydrated) cobalt oxides. From this and earlier experiments it was concluded that the La0.5Ba0.5CoO3 electrode is activated by a (possibly diffusion-controlled) oxidation, but a further anodization at high overpotentials leads to passivation with loss of activity for the oxygen evolution. The activity is regained by lowering the overpotential.