Heterostructured Ni(OH)_2-Co(OH)_2 composites on 3D ordered Ni-Co nanoparticles fabricated on microchannel plates for advanced miniature supercapacitor

摘要

Silicon microchannel plates (Si-MCPs) coated with a layer of nickel cobalt alloy (NCA) constitute an excellent substrate for miniature supercapacitors. Nanoscale Ni(OH)_2-Co(OH)_2 composite particles serving as the active materials are electrodeposited on ordered three-dimensional (3D) NCA/Ni/Si-MCPs and the Ni(OH)_2-Co(OH)_2 composites have different structures depending on the amount of Co(OH)_2 in Ni(OH)_2. The nickel hydroxide synthesized from a water-acetone 0.1 M Ni(NO_3)_2·6H_2O solvent has a compact structure, but that from a 0.1 M Ni(NO_3)_2·6H_2O solvent containing 5% Co(NO_3)_2·6H_2O is loosely packed with nanoparticles and that from a 0.1 M Ni(NO_3)_2·6H_2O solvent containing 10% Co(NO_3)_2·6H_2O contains many nanoparticles. Addition of Co(NO_3)_2·6H_2O results in a smooth morphology. The smooth structure is also observed from active materials produced in 20% and 30% Co(NO_3)_2·6H_2O solvents. Five types of electrode materials are investigated from the perspective of electrochemical capacitors by conducting cyclic voltammogram, galvanostatic charge-discharge measurements, and electrochemical impedance spectroscopy. In this experiment, the highest specific capacitance of 7.8 F cm~(-2) is achieved in the samples prepared in 10% Co(NO_3)_2·6H_2O at a discharge current density of 20 mA cm~(-2). It is much better than 1.46 F cm~(-2) observed from previous attempts and the materials have excellent capacity retention.