Nanoporous Anodic Bismuth Oxide for Electrochemical Energy Storage

Abstract

Thin films of nanoporous bismuth oxide were synthesized by a simple electrochemical anodization of bismuth substrate. Annealing the anodic nanoporous Bi 2 O 3 at 240 °C for 2 h resulted in stabilization of the β-Bi 2 O 3 phase that has an n-type conductivity. Longer annealing times resulted in partial formation of the more stable α-Bi 2 O 3 phase that showed monoclinic lattice structure and p-type semiconductivity. Samples containing predominantly the β-Bi 2 O 3 phase showed higher capacitance (1064 mF/cm 2 ) than the samples containing a mixture of α-Bi 2 O 3 + β-Bi 2 O 3 phases (787 mF/cm 2 ) at a current density of 10 mA/cm 2 . The higher capacitance of the samples annealed at 240 ⁰C for 2 h could also be attributed to higher charge carrier density than that of 6 h annealed sample.