Carbon-coated MoO2 nanoclusters anchored on RGO sheets as high-performance electrodes for symmetric supercapacitors

Abstract

A carbon-coated molybdenum dioxide-reduced graphene oxide (RGO@MoO₂/C) composite was synthesized as a high-performance electrode for supercapacitors via a facile hydrothermal method. In this composite, RGO not only provided high conductivity to benefit effective electron transfer, but also offered nucleation sites to load in situ formed MoO₂/C nanoparticles. The MoO₂@C nanoparticles interconnected with each other forming nanoclusters and were anchored uniformly on RGO sheets instead of self-agglomerating into large aggregates. This allowed more MoO₂ grains to gain easy access to both the conductive network and the electrolyte for efficient electron and ion transfer. Moreover, this effect was achieved after the addition of a rather small amount of GO (5 wt%), which allowed high MoO₂/C loading to contribute to the overall capacitance. When the RGO@MoO₂/C composite was evaluated as an electrode material for supercapacitors, a synergistic effect was exerted with high specific capacitance (1224.5 F g⁻¹ at 1 A g⁻¹) and large reversibility (92% capacitance retention after 3000 cycles), both of which were of great advantage over individual MoO₂/C composite. RGO@MoO₂/C was also used to construct a symmetric supercapacitor, which showed enhanced voltage profiles and could light an LED device for dozens of minutes, thus confirming its excellent electrochemical performance.