Preparation of porcupine-like Bi2O3 needle bundles by anodic oxidation of bismuth

•Breakdown anodization of Bi substrates in H2SO4 electrolyte was carried out.•Bismuth aqua sulfate hydroxide needle bundles were produced as a result.•Upon subsequent annealing in air at 250 °C, tetragonal β-Bi2O3 needles were formed.•The anodic growth of the needles was investigated in detail.

A new Bi2O3 structure resembling bundles of needles was prepared by anodic oxidation of a bismuth substrate in H2SO4 electrolyte followed by annealing in air. Needle growth occurred on the timescale of minutes. The resulting porcupine-like needle bundles were characterized using SEM and XRD before and after annealing. The as-grown needles consisted of bismuth aqua sulfate hydroxide; however, upon annealing at 250 °C in air, tetragonal β-Bi2O3 was produced without any morphological change.

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