Direct growth of three-dimensional nanoflower-like structures from flat metal surfaces

Here we report on a facile top-down approach for the direct growth of Co3O4 hierarchical nanoflowers from a bulk Co surface via chemical etching and thermal annealing. The effect of the annealing temperature was investigated, showing that amorphous Co3O4 was formed at 250 degrees C, while crystalline Co3O4 with notable oxygen vacancies was created at 550 degrees C. The formed 3D nanostructures exhibited excellent oxygen evolution reaction (OER) activities with a low overpotential of 0.34 V at 10 mA cm(-2) and high durability. The proposed novel approach was further demonstrated by the direct growth of 3D NiO and CuO nanostructures on Ni and Cu substrates.

Automated summary

In this study, a facile top-down approach was developed to directly grow Co3O4 hierarchical nanoflowers from a bulk Co surface via chemical etching and thermal annealing. The annealing temperature was found to have a significant effect on the formation of Co3O4, with amorphous Co3O4 formed at 250 degrees C and crystalline Co3O4 with notable oxygen vacancies created at 550 degrees C. The resulting 3D nanostructures exhibited excellent oxygen evolution reaction (OER) activities and durability.