From 1D to 2D: dopamine constructed 2D NiCo-hydroxide nanosheets/graphene composites for high-performance supercapacitors

Abstract

A dopamine (DA)-based construction strategy is reported for designing high performance 2D NiCo-hydroxide nanosheets/graphene@polydopamine (NiCo-OH/G@PDA) composites. The strong coordination bond energies between the dopamine and metal ions are crucial for PDA to induce the formation of NiCo-OH nanosheets. The 2D structured NiCo-OH nanosheets can shorten the transportation path of charge and electrons and provide abundant redox reaction sites to enhance the pseudocapacitance. The high redox activity of N/O groups of PDA can also boost the pseudocapacitance to enhance the electrochemical performance. Moreover, the existing graphene in the NiCo-OH/G@PDA composite may construct a conductive network to boost redox reactions. Owing to the synergic effects of 2D NiCo-OH nanosheets, PDA and graphene, the prepared NiCo-OH/G@PDA with an optimized amount of DA delivers a high capacity of 1520 F g⁻¹ at 1 A g⁻¹ with an excellent rate capability of 68% at 50 A g⁻¹ and good cycling stability. Furthermore, the assembled asymmetric supercapacitor exhibits a high energy density of 47 W h kg⁻¹ at a power density of 1600 W kg⁻¹. This work can provide a promising novel strategy for the development of 2D metal hydroxides for high-performance supercapacitors.