3D nitrogen-doped graphene/Co(OH)2-nanoplate composites for high-performance electrochemical pseudocapacitors

Abstract

We report a simple hydrothermal synthesis of nanocomposites, constructed by 3D nitrogen-doped graphene (NG) networks with hexagonal Co(OH)₂ nanoplates, which are optimized for applications as electrochemical pseudocapacitor materials. Single-crystalline Co(OH)₂ plates are distributed homogeneously inside the conductive interconnected NG networks. The 71% Co(OH)₂ weight content achieves a capacitance of 952 F g⁻¹ at 1.0 A g⁻¹, more than triple that of the pure NG and nearly four times that of Co(OH)₂ plates; moreover, this value exceeds the recently reported values for 2D graphene/Co(OH)₂ composites. Capacitance retention over 2000 cycles is still high as 95%. The improvements are attributed to the regular morphology of Co(OH)₂ and the 3D porosity, which prevents the stacking of the Co(OH)₂ plates as well as the composite, and the continuously connected pores and highly conductive NG networks, which facilitate electron and ion transport.