Stirring-assisted solvothermal synthesis of NGr-Co3O4 nanostructures towards oxygen evolution reaction

A solvothermal process has been used to synthesize Co3O4-nanographitic flakes. Cobalt acetate precursor in ethylene glycol with and without assistance of stirring during the solvolthermal synthesis at 180 °C is converted to Co3O4 nanoparticles-nanographitic flakes. Then, a DC electrophoretic deposition technique is applied to fabricate the Co3O4 nanoparticles-nanographitic flake layers on the stainless steel plates. The oxygen evolution reaction (OER) activities of the fabricated electrocatalysts are characterized by employing electrochemical measurements in an alkaline solution. The composite electrocatalyst layer, which is prepared without the effect of the stirring demonstrates better OER performance compared to its counterpart fabricated with the assistance of the stirring. This is likely due to the fast mass transport of cobalt species during stirring, leading to much agglomeration of Co3O4 nanoparticles-nanographitic flakes. The fabricated Co3O4-nanographitic flakes without stirring exhibits an excellent onset of 1.53 versus reversible hydrogen electrode (RHE) and a current density of 125 mA/cm2 at 1.65 V owing to the proper deposition of Co3O4 nanoparticles on the nanographitic flakes.