Water oxidation by Ni(1,4,8,11-tetraazacyclotetradecane)2+ in the presence of carbonate: new findings and an alternative mechanism.

Herein, the water-oxidation reaction by Ni(1,4,8,11-tetraazacyclotetradecane)2+ in the presence of carbonate was reinvestigated by scanning electron microscopy, energy dispersive spectrometry, electrochemistry, and high-resolution spectroelectrochemical and hydrogen nuclear magnetic resonance spectroscopy methods. These methods showed that the complex was not stable under water-oxidation conditions. The role of nanosized particles or Ni ions on the surface of the electrode for water oxidation was studied and it is proposed that Ni ions or Ni oxides on the surface of the electrode are at least one of the candidates contributing to the observed catalysis.