One-step hydrothermal fabrication of strongly coupled Co3O4 nanosheets–reduced graphene oxide for electrochemical capacitors

Abstract

In the work, we developed a one-step synthetic strategy to prepare a strongly coupled Co₃O₄ nanosheets–reduced graphene oxide (Co₃O₄ NSs–rGO) hybrid, and further utilized it as a promising electroactive material for electrochemical capacitors (ECs). During the hydrothermal procedure, the GO was reduced and Co₃O₄ NSs were in situ grown on the rGO sheets simultaneously due to the electrostatic interaction between the Co²⁺ and GO sheets. Electrochemical characteristics indicated that the Co₃O₄ NSs–rGO hybrid with ∼7.2 wt% Co₃O₄ loading delivered a specific capacitance (SC) of 187 F g⁻¹ at 1.2 A g⁻¹. Furthermore, the SC degradation of the hybrid was ∼6 and 9% at constant current densities of 1.2 and 5 A g⁻¹ after 1000 continuous charge–discharge cycles, demonstrating its desirable electrochemical stability. The synergetic effect of nanoscale size and good redox activity of the Co₃O₄ NSs combined with the high electronic conductivity of the rGO resulted in the enhanced electrochemical utilization at high rates. In addition, an activated carbon/Co₃O₄ NSs–rGO asymmetric EC was further fabricated, and exhibited a specific energy density of ∼13.4 W h kg⁻¹, specific power density of ∼2166 W kg⁻¹ and striking electrochemical stability with ∼11% SC degradation after 1000 cycles.