Synthesis of 3D hierarchical porous Ni–Co layered double hydroxide/N-doped reduced graphene oxide composites for supercapacitor electrodes

Abstract

In this work, three-dimensional porous Ni–Co layered double hydroxide nanosheets are vertically decorated on N-doped reduced graphene oxide via a simple one-step microwave-assisted hydrothermal process. The incorporated N-doped reduced graphene oxide brings the following advantages: firstly, the improved hydrophilicity of the N-doped reduced graphene oxide offers more nucleation sites to grow layered double hydroxide nanosheets on its surface. Secondly, the addition of N-doped reduced graphene oxide can greatly enhance the conductivity and specific surface area of the composites, thus resulting in better capacitance performance and improved rate capability. This composite possesses a high specific capacitance of 1720 F g⁻¹ at a current density of 3 A g⁻¹ and retains 960 F g⁻¹ at a high current density of 50 A g⁻¹. The asymmetric supercapacitor assembled by adopting the prepared composites as the positive electrode and activated carbon as the negative electrode achieves a high energy density of 31.2 W h kg⁻¹ at the power density of 0.354 kW kg⁻¹ and a good long-time cycling stability (83% retention over 10 000 cycles).