Unveiling the Origin of Unusual Pseudocapacitance of RuO2路nH2O from Its Hierarchical Nanostructure by Small-Angle X-ray Scattering

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• 作者：Noboru Yoshida ; Yuki Yamada ; Shin-ichi Nishimura ; Yojiro Oba ; Masato Ohnuma ; Atsuo Yamada
• 刊名：The Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：June 13, 2013
• 年：2013
• 卷：117
• 期：23
• 页码：12003-12009
• 全文大小：405K
• 年卷期：v.117,no.23(June 13, 2013)
• ISSN：1932-7455

文摘

Hydrous ruthenium oxide (RuO₂路nH₂O) has inherent proton鈥揺lectron mixed-conductive nature and offers huge pseudocapacitance (>700 F g^鈥?), having attracted the attention of many capacitor engineers. However, the origin of the anomalous pseudocapacitance, exhibiting a strong maximum at a specific narrow optimum annealing temperature of ca. 150 掳C, has yet to be understood. Here we show a long-awaited explanation for this mystery based on its hierarchical nanostructure unveiled by small-angle X-ray scattering (SAXS). The striking contrast in X-ray atomic scattering factors enables SAXS to exclusively probe heavy RuO₂ in subnano- to nanoscale, dispersed in confined water. We demonstrate that the surface area of the first aggregate of subnano primary RuO₂ particles dominates the accessible number of proton and hence pseudocapacitance, providing critical insights into the nanoarchitectural design of high-performance electrodes for electrochemical capacitors.