Electrochemical surface enlargement of a niobium foil for electrolytic capacitor applications

Electrochemical etching for surface enlargement of niobium was investigated for electrolytic capacitor applications. We obtained a niobium capacitor with a capacitance of 271.4 μF/cm2, which is approximately four times larger than a conventional aluminum capacitor. The enhanced capacitance was attributed to surface enlargement by a factor of more than 40, which was prepared by the etching of niobium at 20 V in propanolic HF (2 wt.%) for 6 h. Electrochemical conditions and their corresponding capacitance are discussed.