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

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.