Enhanced supercapacitor performance by fabricating hierarchical nanoporous nickel/nickel hydroxide structure

• Hierarchical porous Ni was fabricated by dealloying Ni15Al85 alloy.
• The efficient space of the hierarchical structure allows more metal oxides formed.
• The hierarchical porous composite exhibits a high areal/volumetric capacitance.

Hierarchical nanoporous Ni with both nanopores (less than 10 nm) and big pores/channels (hundreds nm) was fabricated by chemically dealloying a diluted Ni15Al85 precursor in 1.0 M NaOH aqueous solutions. Due to the active property of nanoscale Ni, the Ni nano-ligaments can be easily converted to Ni/Ni(OH)2 core–shell-like nano-composite by electrochemical oxidation. Compared with uniform nanoporous Ni, the hierarchical nanoporous Ni provides more void space and allows the formation of more active Ni hydroxides inside. Consequently, the hierarchical nanoporous metal/metal hydroxides composite exhibits a high areal capacitance (~4.76 F cm−2) with good rate performance and cycling stability.