Oxygen evolution on Co-Cu-Zn ternary spinel oxide-coated electrodes in alkaline solution - Integration of statistical, electrochemical, and textural approaches

A systematic investigation of Co-Cu-Zn ternary oxide-coated electrodes fabricated by thermal decomposition is performed through means of statistical, electrochemical, and textural approaches. Integration of these methods clearly reveals that ternary oxides prepared from the precursors containing 70 to 85% Co, 10 to 20% Cu, and 2 to 10% Zn by molar proportion possess both the highest apparent and electrocatalytic activities for oxygen evolution. The intercalation of both Cu2+ and Zn2+ in the Co3O4 matrix, resulting in changes of the binding energy of the Co species and the distribution of various cations, can independently increase or decrease the reversibility of the Co(IV)/Co(III) and thus, respectively, enhances or depresses the electrocatalytic activity of cobaltite spinel oxides. The electrocatalytic activity of the Co(IV)/Co(III) for oxygen evolution is directly proportional to its redox reversibility. Results of both energy dispersive spectroscopy and x-ray photoelectron spectroscopy show that an inhomogeneous distribution of the cations occurs on these mixed oxides during thermal decomposition.