Morphological Transformations during In Situ Electrochemical Generation of 2-Dimensional Co3O4Hexagonal Nanoplates

In situ electrochemical generation of 2-dimensional Co 3 O 4 (2D-Co 3 O 4 ) nanoplates has been achieved by anodizing CoO x /Co precursors in 1 M KOH solution. X-ray diffraction characterization suggests that the CoO x /Co precursor is oxidized to Co 3 O 4 before the onset potential of oxygen evolution reaction (OER). Scanning electron microscopy shows that instead of retaining its original morphology, the irregular-shaped nanoparticles undergo a morphological transition into hexagonal nanoplates during the oxidation process. The mechanism of the morphological changes is discussed and a two-step topotactic transformation pathway from Co(OH) 2 to CoOOH to Co 3 O 4 is proposed. Amorphization and recrystallization of the catalysts are also found at different stages of the electrochemical measurements. The 2D-Co 3 O 4 nanoplates exhibit high OER catalytic activity.