Tailoring the structure of supported δ-MnO2 nanosheets to raise pseudocapacitance by surface-modified carbon cloth

Abstract

Coupling electrode composed of carbonaceous materials and metal oxides can effectively raise pseudocapacitance; however, due to the weak interaction between carbonaceous materials and metal oxides, structural control of the resultant coupling electrode remains a great challenge. Herein, surface-modified carbon cloth (SMCC), which is obtained by carbonizing the hydrothermal products of cetyltrimethylammonium bromide and glucose solution on carbon cloth (CC), is employed to regulate in-situ growth of δ-MnO2 in a KMnO4 and H2SO4 solution at hydrothermal condition. Structural characterizations indicate that surface modification renders SMCC to possess an oxygen-species-rich superhydrophilic surface, which in turn enables the supported δ-MnO2 to form the dense ultrathin nanosheets and abundant oxygen-vacancy (Vo) structure. Electrochemical tests demonstrate that the MnO2/SMCC can exhibit a specific capacitance of 508 F g−1 (792.5 C g−1) at 1 A g−1 under working potential range from −0.3 to 1.26 VAg/AgCl in three-electrode system, outperforming previously-reported δ-MnO2-based materials. Further, the detailed structural investigations identify that the oxygen species on SMCC dominate the generation of Vo in δ-MnO2 by reducing thickness and interface bonding, and the Vo in δ-MnO2 improves the pesudocapacitance by promoting the transition of Mn2+ to Mn4+.