Porous hexagonal cobalt oxyhydroxide sheets with attached nickel hydroxide nanoparticles as electrode materials for electrochemical supercapacitors

Abstract

Ni(OH)₂ nanoparticles were self-assembled on porous hexagonal CoOOH sheets by a simple cathodic electrophoresis in CoOOH suspension with nickel nitrate additive. A significant shift of redox peaks in the Ni(OH)₂/CoOOH composite electrodes compared with the bare Ni(OH)₂ electrode indicated the formation of mixed Co–Ni hydroxide layers. The amount of Ni(OH)₂ nanoparticles on the porous CoOOH sheet dominated the capacitive behavior of the composite electrodes. The Ni(OH)₂/CoOOH electrode with 20 wt% of Ni(OH)₂ prepared in 1 mM nickel nitrate showed the highest specific capacitance and good cycle-life stability, its specific capacitance discharged at 1 A g⁻¹ could reach as high as 1537 F g⁻¹ much higher than that of bare CoOOH (52 F g⁻¹) and Ni(OH)₂ (785 F g⁻¹) electrodes. A noticeable improvement in capacitive behavior resulted from the porous conductive CoOOH sheets that facilitated the transport of electron and electrolyte.