Structural Modification of Self-Organized Nanoporous Niobium Oxide via Hydrogen Treatment

Niobium pentoxide (Nb2O5) is an interesting material with applications in Li battery and hybrid capacitor electrodes. The main limitation of this material is its low electronic conductivity. In this study, H2 treatment is introduced to address this issue. Self-ordered Nb2O5 films were prepared by anodizing Nb foils and subsequently treating them in a H2 atmosphere. Electron microscopy revealed that the Nb2O5 film had a hierarchical porous microstructure consisting of macropores and mesopores. X-ray diffraction analysis showed that the crystal structure could be changed by the H2 treatment compared to the air treatment. Oxygen deficiencies in the Nb2O5 film were induced by the treatment, as confirmed by X-ray photoelectron spectroscopy. Mott–Schottky analysis was performed and indicated that the electronic conductivity of the material was significantly improved by the oxygen deficiencies. Thus, the electrochemical Li storage kinetics in porous Nb2O5 films can be greatly enhanced by H2 treatment.