Measurements of the oxygen evolution reaction have been made on eighteen substituted perovskites containing first‐row transition metal ions. Rates are reported at equilibrium and at an overpotential of 0.3V. Electrode kinetic parameters are given, including roughness factors. The rate does not depend on semiconductor‐type properties. It increases as the pH of zero charge, at which the occupancy of OH− and H+ at the interface becomes equal, moves in an alkaline direction, with decrease of magnetic moment, with decrease of stability of the perovskite lattice, with decrease of the enthalpy of formation of the transition metal hydroxides, and with increase in the number of d‐electrons in the transition metal ion. The accuracy of the roughness factor measurements are affected by weakness in knowledge of true double layer capacities. The value assumed here, 60 μF cm−2, may be accurate to only ± 100%. Models are given which suggest that the pores are active throughout. The correlations between the rate and electronic properties are consistent with rate‐determining steps which involve desorption of OH radicals, e.g., M−‐OH+OH+→normalr.normald.normals.Mnormalz…H2O2+e−. An MO discussion suggests that the electrocatalysis increases with increased occupancy of the antibonding orbitals of MZ‒OH. Earlier interpretations include the concept that an increase of the rate occurs because of increasing overlap between the eg orbitals of the transition metal ion and the spσorbital of O. However, this theory is based on only three different materials, in which rate‐determining step changes. An interpretation based upon nonstoichiometry is shown to be consistent with observed trends, but insufficient to explain their magnitude. The electrical and chemical contributions to the rate are analyzed. The value of agr; is related via bond strength considerations to the MZ‒OH bond strengths. The relative electrocatalysis discussed is limited to an overpotential which corresponds to a practical range of rates on the faster catalysts. A volcano relation for oxygen evolution on perovskites seems likely. Future electrocatalysts are predicted.

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In this laboratory, a systematic investigation of the electrocatalysis of oxygen evolution on the perovskite-type oxides has been made (I).The purpose of this communication is to report a favorable kinetics for oxygen evolution observed on pure lanthanum nickelate electrodes (2).In our studies, lanthanum nickela~e crystals were synthesized by a coprecipitation technique. The starting materials were 99.999% pure La(NO3)3.6H20 and Ni(NO3)2.6H20. The precipitates were made by adding IM NaOH, and were separated quickly by a centrifuge technique. Thedried powder was then put in a furnace at 800~ in an 02 atmosphere for 16 hours. The formation of a perovskite structure was confirmed by X-ray diffraction analysis. The electrode was prepared by pressing the powder into a pellet, and then sintered at 750~ in an 02 atmosphere for 48 hours. No attempts were made to mix perovskite powder with a binder, although this approach has been frequently used in previous works.

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