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Paper
J. Mater. Chem., 2010, 20, 390 - 398, DOI: 10.1039/b915370e
Hybrid MnO2–disordered mesoporous carbon nanocomposites: synthesis and characterization as electrochemical pseudocapacitor electrodes
Mehul N. Patel, Xiqing Wang, Brian Wilson, Domingo A. Ferrer, Sheng Dai, Keith J. Stevenson and Keith P. Johnston
MnO2–mesoporous carbon hybrid nanocomposites were synthesized to achieve high values of redox pseudocapacitance at scan rates of 100 mV s-1. High-resolution transmission electron microscopy (HRTEM) along with energy dispersive X-ray spectroscopy (EDX) demonstrated that
1 nm thick MnO2 nanodomains, resembling a conformal coating, were uniformly distributed throughout the mesoporous carbon structure. HRTEM and X-ray diffraction (XRD) showed formation of MnO2 nanocrystals with lattice planes corresponding to birnessite. The electrochemical redox pseudocapacitance of these composite materials in aqueous 1 M Na2SO4 electrolyte containing as little as 2 wt% MnO2 exhibited a high gravimetric MnO2 pseudocapacitance (CMnO2) of 560 F gMnO2-1. Even for 30 wt% MnO2, a high CMnO2 of 137 F gMnO2-1 was observed at 100 mV s-1. Sodium ion diffusion coefficients on the order of 10-9 to 10-10 cm2 s-1 were measured using chronoamperometry. The controlled growth and conformal coating of redox-active MnO2–mesoporous carbon composites offer the potential for achieving high power energy storage with low cost materials.
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