Electrochemically-deposited nanostructured Co(OH)2 flakes on three-dimensional ordered nickel/silicon microchannel plates for miniature supercapacitors

Silicon microchannel plates (Si-MCPs) coated with a nickel layer are an excellent substrate in miniature supercapacitors. Nanometer-sized Co(OH)2 flakes serving as the active materials are electrodeposited on ordered three-dimensional (3D) Ni/Si-MCPs and the Co(OH)2 flakes have different structures depending on the solvent used. The cobalt hydroxide synthesized from a de-ionized water solvent is composed of compact nano-flakes, whereas that synthesized from an alcohol containing solvent is composed of loosely packed nano-flakes, and that from acetone are nano-flakes with nano-particles. The three types of electrode materials are investigated from the perspective of electrochemical capacitors by means of cyclic voltammogram, galvanostatic charge–discharge measurements and electrochemical impedance spectroscopy. The highest specific capacitance of 6.90 F cm−2 is achieved from the samples prepared in acetone at a discharge current density of 10 mA cm−2 and it is much better than the 1.46 F cm−2 observed in previous studies, thus demonstrating excellent capacity retention.