Co3O4 nanorods with prevalent oxygen-vacancies confined by PDA-RGO nanosheets for excellent performances in supercapacitors

Abstract The rich oxygen-vacancies (OVs) on transition metal oxides are favorable for charge storage in supercapacitors, but are subjected to deactivation during charge-discharge cycles. Herein, we report that Co3O4@polydopamine-reduced graphene oxide (Co3O4@PDA-RGO) nanocomposite could relieve the deactivation problem via the self-reviving of OVs. Besides the high specific surface area and ion/electron conductivities, Co3O4@PDA-RGO provides a robust framework to disperse Co3O4 nanorods, and the oxygen atoms in the vicinity of OVs account for 46.2% of oxygen-species. Especially, the resultant OVs can survive the rigorous charge-discharge cycles by virtue of the reversible redox with the aid of PDA-RGO. Given the advantageous structural characteristics, a high specific capacitance of 1562 F g-1 (781 C g-1) can be delivered at current densities of 0.5 A g-1 and retain to 771 F g-1 (385.5 C g-1) at 20 A g-1 by the Co3O4@PDA-RGO electrode. Moreover, 91 % of its initial capacitance can be maintained after 10,000 consecutive charge-discharge cycles. The asymmetric supercapacitor, assembled by the Co3O4@PDA-RGO electrode and an activated carbon electrode, delivers a high energy density of 46.1 Wh kg-1 at 800 W kg-1. This study paves an efficient avenue to synthesize self-reviving OV on metal oxides for the potential applications in supercapacitors.