Topotactic transition of α-Co(OH) 2 to β-Co(OH) 2 anchored on CoO nanoparticles during electrochemical water oxidation: synergistic electrocatalytic effects.

Herein, we report a single step, anionic surfactant-assisted, low temperature-hydrothermal synthetic strategy of CoO nanoparticles anchored on β-Co(OH) ₂ nanosheets which show a low overpotential (295 mV @ 10 mA cm ^-2 ) for the oxygen evolution reaction (OER). They also demonstrate much better kinetic parameters compared to the state-of-the-art RuO ₂ . Interestingly, under the OER operational conditions (in alkaline medium), the topotactic transformation of α-Co(OH) ₂ to a stable Brucite-like β-Co(OH) ₂ phase leads to a synergistic interaction between the β-Co(OH) ₂ sheets on the CoO nanoparticles for enhancing the OER electrocatalytic activity.