Heterostructured Ni(OH)2-Co(OH)2 composites on 3D ordered Ni-Co nanoparticles fabricated on microchannel plates for advanced miniature supercapacitor

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(NO3)2⋅6H2O solvent has a compact structure, but that from a 0.1 M Ni(NO3)2⋅6H2O solvent containing 5% Co(NO3)2⋅6H2O is loosely packed with nanoparticles and that from a 0.1 M Ni(NO3)2⋅6H2O solvent containing 10% Co(NO3)2⋅6H2O contains many nanoparticles. Addition of Co(NO3)2⋅6H2O results in a smooth morphology. The smooth structure is also observed from active materials produced in 20% and 30% Co(NO3)2⋅6H2O 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(NO3)2⋅6H2O 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.