Surfactant-free hybridization of transition metal oxidenanoparticles with conductive graphene for high-performance supercapacitor

Abstract

In order to improve specific capacitance and limit electrical resistance, high-quality exfoliated graphene decorated with transition metal (Fe, Mn, Co) oxide nanoparticles (NPs) has been successfully synthesized without the use of surfactantvia a simple, general, environmentally-friendly chemical process. The specific capacitance of as-prepared graphene/Mn₃O₄ composite reach 239.6 F/g, when employed as the anode material in neutral NaCl electrolyte solutions (cf. 98.2 F/g for pristine graphene and 141.4 F/g for pure Mn₃O₄ NPs), which indicate the synergetic effects from both graphene and attached Mn₃O₄ NPs. Moreover, the high conductivity of graphene eliminates the need for conductive carbon black as fillers. The current density of graphene/Mn₃O₄ reached as high as 4.5 A g⁻¹ which is much higher than that of graphene oxide (GO) or reduced GO-based composites. This significant enhancement of capacitance and current density was attributed to the surfactant-free approach to hybridize graphene with transition metal oxide NPs, the excellent conductivity of pristine graphene combined with its large surface area, as well as a uniform distribution of NPs on the clean surface of conductive graphene. Thus the low-toxicity, inexpensive graphene-based hybrids show promising utility as high current density electrode materials for supercapacitor applications.