Rational design of a sandwiched structure Ni(OH)2 nanohybrid sustained by amino-functionalized graphene quantum dots for outstanding capacitance

Abstract

The rational structure design of nanohybrids plays a vital role in the supercapacitor performance of electrode materials. Herein, a novel sandwiched structure based on Ni(OH)2 and amino-functionalized graphene quantum dots (Ni(OH)2/af-GQDs) is prepared via a facile green strategy. The layered Ni(OH)2 nanosheets are spaced by amino groups from af-GQDs to afford a sandwiched configuration with an enlarged pore diameter of 1.8 nm, which leads to the decrease of random aggregation of Ni(OH)2 nanosheets and dramatically facilitates the ion transport, thus contributing to the increased surface area and improved electrochemical capacitance. Besides, the introduction of af-GQDs leads to enhanced electrical conductivity and better cycling stability as well as contributing additional electrochemical double-layer capacitance, resulting in an outstanding specific capacitance of 2653 F g−1 at 1 A g−1. An asymmetric supercapacitor (ASC) based on Ni(OH)2/af-GQDs and electrochemical-exfoliated graphene (EG) is assembled, exhibiting a wide potential window range, a high energy density, and an excellent cycling stability with 90.15% capacitance retention. These results definitely demonstrate the great potential of Ni(OH)2-based hybrid materials in the development of high-performance supercapacitors.