Tunable electrochemical preparation of cobalt micro/nanostructures and their morphology-dependent wettability property

A versatile cobalt micro/nanostructure preparation method via a facile electrochemical growth approach is reported in this study. Based on the existing theoretical analysis, the various crystal growth parameters, including the potential, concentration and temperature, act as parameters to impact the metallic crystal growth rate and the resultant morphology. These parameters were varied to elucidate the growth rate and morphology changes. Electron microscopy technique was applied to reveal the corresponding crystal morphology, which demonstrates that the potential can consequently impact the crystal shapes formed, from bump to flower and dendrite shapes. However, in the current experiments, the morphology achieved by changing the concentration and temperature was a dendritic structure, which suggests that the growth conditions promoted a dendritic structure formation regime. Based on the structures grown at various potentials, without further surface modifications, a morphology-dependent wettability trend exhibited from the superhydrophobic to superhydrophilic structures. The superhydrophobicity stems from the small contact areas of the tips of the flower-like structure. Meanwhile, the superhydrophilicity is due to the nanometer-scale channels existing in the hierarchical structures of the dendritic crystals, in which the capillary effect draws water droplets to spread on the surface rapidly.