Novel Bi2O3 nanoporous film fabricated by anodic oxidation and its photoelectrochemical performance

Novel bismuth oxide (Bi₂O₃) nanoporous films were fabricated through anodization of bismuth foil in electrolytes containing glycol, ammonium sulfate ((NH₄)₂SO₄) and deionized (DI) water. Scanning electron microscopy analysis indicated that morphology of the anodized bismuth foil changed markedly along with the changing of oxidation time, water content, electrolyte concentration, temperature, and applied voltages. The optimized morphology was obtained when bismuth was anodized at 20 V, 40 °C for 40 min in glycol solution containing 0.3 wt% (NH₄)₂SO₄ and 5 wt% DI water. The composition and crystal structure of the samples formed in the optimized conditions were characterized by energy-dispersive spectroscopy and X-ray diffraction. Results showed that the as-prepared nanoporous structures were amorphous. β-Bi2O3 was obtained when the samples were annealed at 200 °C. The photocurrent response experiments demonstrated that the Bi₂O₃ nanoporous film can generate photocurrent as large as 2.893 and 6.980 μA/cm² under 0 and 0.5 V bias voltage versus saturated calomel electrode, respectively.