Crystalline Vanadium Pentoxide with Hierarchical Mesopores and Its Capacitive Behavior

• Published in: Chemistry, an Asian journal an Asian journal, 2006-11, Vol.1 (5), p.701-706
• Main Authors: Liu, Hongtao, He, Ping, Li, Zhiying, Sun, Danzi, Huang, Haiping, Li, Jinghong, Zhu, Guoyi
• Format: Article
• Language: English
• Subjects: capacitance; ionic liquids; mesoporous materials; template synthesis; vanadium
• ISSN: 1861-4728; 1861-471X
• DOI: 10.1002/asia.200600169

Crystalline vanadium pentoxide with hierarchical mesopores was synthesized by using a CTAB/BMIC cotemplate (CTAB=cetyltrimethylammonium bromide, BMIC=1‐butyl‐3‐methylimidazolium chloride). The material was fully characterized by SEM, TEM, N2 adsorption–desorption, XRD, XPS, and CV methods. By elaborate adjustment of the template proportions, the distribution and size of the hierarchical pores were tuned successfully. CTAB cationic surfactant contributed more to the larger mesopores, whereas BMIC ionic liquid was beneficial in forming the smaller nanopores. The vanadium‐containing anions combined with CTA+ micelles and BMI+ rings through electrostatic interactions. The CTA+–O(VO)O−–BMI+ entities built up an orderly array, which finally formed the hierarchical mesoporous framework during thermal treatment. The mesoporous vanadium pentoxide directed by the cotemplate of CTAB/BMIC=1:1 showed many orderly crystalline structures and demonstrated a large capacitance (225 F g−1); it is thus a promising material for electrochemical capacitors. Two alternative solutions to the disappearance of capacitance due to insertion of K+ are proposed in view of possible future applications. Two's better than one: The cotemplate consisting of a cationic surfactant called CTAB and an ionic liquid called BMIC can be used to synthesize crystalline vanadium pentoxide with hierarchical mesopores. The product formed with equimolar quantities of the template reagents has a large capacitance and could be useful in electrochemical capacitors.