Fabrication of multilayer Nb 2 O 5 nanoporous film by anodization of niobium foils

Multilayer Nb 2 O 5 nanoporous films were successfully synthesized on Nb surfaces by the control anodization process in ethylene glycol containing 4 vol% HF and 2 vol% H 2 O 2 electrolyte. The nanoporous films are characterized in detail by field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The Nb 2 O 5 nanoporous films have a multilayer morphology with the side wall thickness of ~5 nm, irregular pores with a diameter of ~25 nm, and a length of up to 7.39 μm, depending on the anodization time. A mechanism for the multilayer Nb 2 O 5 nanoporous formation was also discussed. These nanoporous materials can be very useful in the fields of solar cells, gas sensors, catalysts, optical filters, and capacitors.