Scalable thermal synthesis of a highly crumpled, highly exfoliated and N-doped graphene/Mn-oxide nanoparticle hybrid for high-performance supercapacitors

Abstract

A scalable thermal method to synthesize a highly crumpled, highly exfoliated and N-doped graphene/Mn-oxide nanoparticle hybrid for high performance supercapacitors has been demonstrated. Reduction of graphene-oxide (GO), nanometer scale crumpling, high level of exfoliation, N-doping of graphene and decoration with Mn-oxide nanoparticles, each of which significantly contributes to a high specific capacitance (958 F g(-1) at 5 mV s(-1)) in a synergetic way, are achieved in a single thermal process, thermal annealing of GO-Gly-Mn(NO3)(2)center dot 4H(2)O mixture at 500 degrees C followed by a rapid quenching with liquid nitrogen. N-doping of graphene is predominantly done in the form of pyrrolic-like and pyridine-like nitrogens, and Mn-oxide nanoparticles are formed on the surface of graphene as MnO2 and Mn3O4. The nanometer scale crumpling of graphene sheets, which is achieved by rapid quenching of graphene in the presence of Mn-oxide nanoparticles on its surface, induces an exceptionally high degree of exfoliation of graphenes and prevents restacking of graphene sheets during a repeated charge-discharge process, providing a high specific surface area (1006 m(2) g(-1)) and high cycle stability (94.1% retention after 1000 cycles), respectively. The simplicity of the synthesis process and the high performance of supercapacitors make it an easily scalable and industrially applicable method.