Synthesis of urchin-like Co₃O₄ spheres for application in oxygen evolution reaction

For oxygen evolution electrocatalysis of water splitting, unique urchin-shaped Co₃O₄ spheres were successfully grown on nickel foam by hydrothermal synthesis of Co(OH)F precursor and subsequent annealing method. The formation process was investigated by the evolution of phase structure and morphology with hydrothermal reaction time. And it can be explained by a 'disks-flowers-urchins' mechanism. Moreover, the Co₃O₄ urchins/NF exhibits considerable catalytic properties. It shows a low overpotential of 308 mV at a current density of 20 mA cm^-2 in alkaline solution. In the meantime, such material has a small Tafel slope of 82.1 mV dec^-1, large electrochemical active surface area and good long-term stability. The obvious promotion of oxygen evolution reaction performance can be attributed to the special morphology and the direct attachment to the substrate, which improve the exposed active sites, lower the internal resistance and accelerate the charge transport. Thus, the Co₃O₄ urchins/NF not only has a great potential promising behavior, but also provides the basis for subsequent performance improvement.