Direct synthesis of electroactive mesoporous hydrous crystalline RuO2 templated by a cationic surfactant

We describe a direct low-temperature, liquid crystal surfactant templating and crystallization route to form quasi-ordered crystalline mesoporous RuO2·0.4H2O. Our method constitutes a direct approach to the crystalline oxide, constructed of nanosized metal oxide building blocks that are assembled to form thin walls. This leads to high surface areas (up to 250 m2 g−1). In our approach, cationic surfactants (i.e., hexadecyl-trimethylammonium chloride, C16TMA+Cl−) serve as pore-directing agents, which can participate in an indirect S+X−I+ interaction mediated by the chloride ion to coordinate a cationic ruthenium nitrosyl precursor. Gentle decomposition of the initially formed mesostructured metal cation–surfactant composite leads to crystallization of the wall structure. The promising electrochemical properties of porous RuO2·xH2O result from a more highly ordered structure and almost tripled surface area (190 m2 g−1) compared to that obtained from the nanocasting method. Crystalline mesoporous RuO2·0.4H2O exhibits high capacitance of 410 F g−1 and good rate capability, whereas the amorphous mesoporous RuO2·1.3H2O displays capacitance over 700 F g−1.