One-step synthesis of self-standing porous Co-doped NiO electrodes for high-performance supercapacitors

Abstract

This work delivers a facile doping strategy to synthesize the self-standing porous Co-doped NiO electrode materials ((Ni,Co)O@np-NiCo/MG) by free-dealloying Ni30Co10Zr60 metallic glass (MG) in HF solution. The typical surface of the dealloyed Ni30Co10Zr60 samples is mainly composed of petal-like and crack regions. It is clearly seen that the spongy-like structure with abundant nanopores is formed in the crack regions. The nanoporous channels provide “expressway” for ion diffusion and Co doping endows the electrode with better electrical conductivity, which improve the electrochemical performance of the electrodes. The Co-doped NiO electrode exhibits a high capacitance (944.4 F cm−3 at 1 A cm−3) and good cycle stability (91.3 % retention after 8000 cycles at 4 A cm−3). Most importantly, a new perspective about the interaction between the Co-doped NiO material and electrolyte ions (OH-) by DFT calculation is addressed in this work. DFT calculations reveal that the Co-doped NiO possesses higher electrical conductivity and outstanding OH- adsorption capability, thus leading to the excellent electrochemical performance. Furthermore, the assembled supercapacitor exhibits a high energy density of 25 mWh cm−3, showing a good promise for application in supercapacitors.