A facile low-temperature synthesis of highly distributed and size-tunable cobalt oxide nanoparticles anchored on activated carbon for supercapacitors

In this report, a facile microwave-assisted depositioneprecipitation method is utilized to prepare uniformly distributed Co sub(3)O sub(4) nanoparticles on the surface of activated carbon (AC) for electrochemical capacitors. The size of the Co sub(3)O sub(4) particles is well controlled ranging from several to tens of nanometers by manipulating the pre-oxidization of the AC. The capacitive performance of the obtained Co sub(3)O sub(4)/AC hybrids is determined by the synergistic effects of electric double layer capacitance from the AC support and psedocapacitance from the anchored Co sub(3)O sub(4) nanoparticles, which is highly dependent on their particle size and loading. The hybrid materials can provide specific capacitance up to 491 F g super(-1) at 0.1 A g super(-1) in a 6 M KOH electrolyte as the average size of the Co sub(3)O sub(4) is 7 nm and the loading is 16.4 wt%. In addition, an excellent electrochemical stability is achieved with an only 11% capacitance degradation after 5000 charge-discharge cycles at a large current density of 5 A g super(-1), demonstrating that solid bindings between the Co sub(3)O sub(4) nanoparticles and AC support have been achieved during the microwave assisted preparation.