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.

424