Capacitor properties of 3D hierarchical structured electrodes prepared by one-step electrodeposition of cobalt nanowires on stainless steel fiber sheets

Redox or pseudo-capacitors using a cobalt (II) hydroxide (Co(OH)2) material have been regarded as promising options for renewable energy storage. In this study, we deposited cobalt nanowires with a Co(OH)2 surface layer on a newly developed stainless steel fiber sheet by a one-step electrodeposition method, without any templates, to form a 3D hierarchical structured electrode. This electrode achieved a specific capacitance of 880 F g−1 at a current density of 1.8 A g−1, which is much higher than the values attained with cobalt-nanowire-deposited stainless steel (200 F g−1) and indium-tin-oxide-coated glass (455 F g−1) plates. Moreover, the cobalt nanowire electrode coupled with a nickel-plated stainless steel fiber sheet exhibited increasing capacitance performance with repeated charge–discharge cycles, eventually developing approximately twice the capacity of the above electrode. These results demonstrate the potential of stainless steel fiber sheets for developing high-performance redox capacitors using a very facile method.