Effect of Co(NO ₃ ) ₂ ·6H ₂ O thermal decomposition temperature on the nano-Co ₃ O ₄ product morphology and electrocatalysis of water oxidation

Herein, we report the electrochemical water oxidation efficiency of nano-Co ₃ O ₄ catalyst samples obtained by the thermal decomposition of Co(NO ₃ ) ₂ ·6H ₂ O at various temperatures (320, 420, 520, and 620 °C). The structural and morphological details of the synthesized samples were determined by employing X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. These studies revealed the formation of well-dispersed nano-Co ₃ O ₄ particles with sizes, shapes, and crystallinity levels that differed for the different decomposition temperatures. The prepared catalysts were immobilized on filter-paper-derived carbon electrodes for checking their electrochemical properties. The electrochemical efficiency levels of the Co ₃ O ₄ catalyst samples were evaluated by employing each of them as an anode to study the water oxidation reaction. The nano-Co ₃ O ₄ sample prepared at 420 °C yielded the highest efficiency and good stability towards the water oxidation reaction. The higher efficiency of this sample was attributed to the relatively small average size and low level of agglomeration of its nanoparticles, and to the high electrochemically active surface area of its electrode. Graphical abstract: Different morphology and crystallinity of nano-Co ₃ O ₄ were prepared by simple and straightforward thermal decomposition of Co(NO ₃ ) ₂ ·6H ₂ O for electrochemical water oxidation. The nano-Co ₃ O ₄ prepared at 420 °C showed the highest efficiency and good stability towards water oxidation. [Figure not available: see fulltext.].