The electrocatalysis of O-2 evolution has been studied at the CoxFe3-xO4 (0 less than or equal to x less than or equal to 1.5), CuxFe3-xO4 (0.1 less than or equal to x less than or equal to 1.5), Co1.5-xMnxFe1.5O4 (0.1 less than or equal to x less than or equal to 0.5), and Co1.5-xNixFe1.5O4 (0.1 less than or equal to x less than or equal to 0.5) anodes in KOH solutions at 25 degrees C. The oxides were obtained at 70 degrees C as precipitate and produced in the him forms on a nickel support by an oxide-slurry painting technique. The study showed that both the electrochemically active area as well as the apparent electrocatalytic activity of the oxide increased significantly with increasing replacement of Fe by Co following maximum with x = 1.5. These properties further enhanced nearly by two-fold with 0.5 mol Mn-substitution in Co1.5Fe1.5O4. 1.0 mol Ni-substitution in the Fe3O4 lattice was also greatly beneficial from the electrocatalytic point of view. In contrast, its substitution (0.1-0.5 mol) in the Co1.5Fe1.5O4 lattice was not. Also, Cu-substitution in the base oxide did not indicate any electrocatalytic effect. The reaction order (p) and the Tafel slope (b) have been observed to vary with the introduction of Co. The electroformation of O-2 on the active electrodes, namely, NiFe2O4, CoFe2O4 and Co1.5Fe1.5O4, exhibited approximately second-order kinetics in OH-concentration.