Fern-shaped bismuth dendrites electrodeposited at hydrogen evolution potentials

Easy fabrication of nanostructured materials with high porosity and high specific surface area has been drawing much scientific interest. Here, we describe a direct electrodeposition of fern-shaped bismuth dendrites at hydrogen evolution overpotentials without any additive and foreign template. A predeposition step was adopted to adjust and control the nucleation and growth of hydrogen bubbles. Subsequently, the simultaneous electrochemical reductions of Bi(3+) and H(+) ions were performed at a constant overpotential. Scanning electron microscopy and transmission electron microscopy characterizations showed that the resultant microporous netlike films consisted of fern-shaped single-crystal bismuth dendrites. The formation mechanism was discussed and ascribed to a "stagnant" template effect of hydrogen bubbles, which limited the lateral growth of fern-shaped dendrites. Such a two-step electrodeposition could also be extended to the nanostructure fabrication of other metals and alloys with high hydrogen overpotentials.