Electrochemical characterization of single-layer MnO2 nanosheets as a high-capacitance pseudocapacitor electrode

A MnO2/carbon composite comprised of single layer MnO2 nanosheets and acetylene black (AB) was assembled by simply mixing a MnO2 nanosheet colloidal suspension and AB suspension. MnO2 nanosheets were synthesized by a one-pot procedure and adsorbed onto AB aggregates as a single layer (monosheets) through electrostatic interactions. The one-pot synthesis ensures no unexfoliated material, unlike previous preparations. Galvanostatic charge–discharge measurements and cyclic voltammetry in organic electrolytes demonstrate that the MnO2/AB composite exhibits an excellent specific capacity and capacitance of 400 mA h g−1 and 739 F g−1, respectively, at a scan rate of 1 mV s−1. The obtained specific capacity considerably exceeds the theoretical capacity; this can be explained by the extremely high fraction of single layer sheets from the one-pot procedure.