Fabrication of three-dimensional nanoporous nickel by dealloying Mg-Ni-Y metallic glasses in citric acid solutions for high-performance energy storage

Free-standing nanoporous nickel (np-Ni) ribbons were directly synthesized by dealloying Mg_90-xNi_xY₁₀ metallic glass ribbons in citric acid aqueous solutions under free conditions. Due to the amorphous nature of the Mg_90-xNi_xY₁₀ precursors, the as-dealloyed samples exhibit a uniform nanoporous structure with the ligament size of ?7 nm. Effects of alloy composition, leaching time, and acid concentration on the resulting nanoporous microstructure were discussed. The lower limit of Ni content in Mg_90-xNi_xY₁₀ precursors was identified to be 20%, below which the nanoporous Ni could not be formed. Besides, a linear relationship was established between the ligament size and the leaching time on a logarithmic scale. The ultrafine structure of the obtained np-Ni was associated with the stabilizing effect of citric acid. The as-dealloyed samples with the naturally formed oxide surface of NiO were directly examined as binder-free electrodes for high-performance supercapacitors.