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

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.