CoOOH ultrathin nanoflake arrays aligned on nickel foam: fabrication and use in high-performance supercapacitor devices

Abstract

CoOOH ultrathin nanoflake arrays grown on nickel foam (NF) have been fabricated by a two-step soft chemical procedure. The ultrathin nanoflakes with a thickness of about 2.7 nm were interconnected with each other and formed a loose and open 3D network structure, providing sufficient exposure of the active sites to an electrolyte. Moreover, the growth mechanism was also investigated. Furthermore, as a supercapacitor material, the CoOOH/NF electrode exhibited ultrahigh specific capacitance (2550 F g⁻¹ at 1.25 A g⁻¹) and good cycling stability (83% of its initial capacitance value was preserved after 5000 charge/discharge cycles at 10 A g⁻¹). Meanwhile, an asymmetric supercapacitor device was assembled with CoOOH/NF as the positive electrode and reduced graphene oxide (rGO) as the negative electrode, displaying an energy density of 49.8 W h kg⁻¹ at a power density of 435 W kg⁻¹. Furthermore, the capacitance retention of the asymmetric supercapacitor after 3000 cycles of charge–discharge at a current density of 7.7 A g⁻¹ is 86%, showing good stability of the asymmetric pseudocapacitor.