A study of photocatalytic, chemical, and electrocatalytic water oxidation on ACo2O4 (A = Ni, Cu, Zn) samples through doping different metal ions

ACo(2)O(4) samples were synthesized as water oxidation catalysts. The samples were characterized by multiple experiments to confirm their uniform morphology, which belongs to the spine] structure (Fd3m space group). The catalytic activity of ACo(2)O(4) samples was investigated under photochemical, chemical, and electrochemical conditions; it follows the catalytic activity order NiCo2O4 > CuCo2O4 > ZnCo2O4. This activity sequence results from different doping metal ions in {Co4O4} motifs, which act as the active sites of water oxidation. Electrochemical impedance spectroscopy and other experimental data demonstrate that ACo(2)O(4) samples doped with different metal ions may influence the rate of charge and electron transport. Therefore, the catalytic activity of water oxidation followed the above order. (C) 2016 Elsevier Inc. All rights reserved.