Micro and nano-architectures of Co<inf>3</inf>O<inf>4</inf> on Ni foam for electro-oxidation of methanol

Spinel Co3O4 material with different morphologies is directly grown on Ni foam by simple hydrothermal method and subsequent calcination processes. The direct growth of binder free active phase of Co3O4 on Ni foam is an effective approach to enhance the electrocatalytic activity of the material. The morphologies of Co3O4 strongly depend on the anion of the precursor salt used. Microflowers, microspheres and nanograss morphologies of Co3O4 are obtained using chloride, sulfate and acetate salts of cobalt, respectively. The BET surface areas of these cobalt oxide materials are found to increase in the order of microflower-Co3O4 (53 m2 g−1) < nanograss-Co3O4 (65 m2 g−1) < microsphere-Co3O4 (100 m2 g−1). The electrocatalytic activity of these Co3O4 materials has been tested for methanol oxidation by cyclic voltammetry and chronoamperometry. All three samples show low onset potentials (0.32–0.34 V) for methanol oxidation. The vanodic peak current of methanol oxidation is found to increase in the order of microflower-Co3O4 (28 A g−1) < nanograss-Co3O4 (34.9 A g−1) < microsphere-Co3O4 (36.2 A g−1) at 0.6 V. This study highlights the significance of the morphology of cobalt oxide in the development of oxide based non-precious electrocatalysts for methanol oxidation.