Fabrication of Three-Dimensional Nanoporous Nickel by Dealloying Mg-Ni-Y Metallic Glasses in Citric Acid Solutions for High-Performance Energy Storage

Abstract

Free-standing nanoporous nickel (np-Ni) ribbons were directly synthesized by dealloying Mg90-xNixY10 metallic glass ribbons in citric acid aqueous solutions under free conditions. Due to the amorphous nature of the Mg90-xNixY10 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 Mg90-xNixY10 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.

Anisotropic Nanoporous Nickel Obtained through the Chemical Dealloying of Y2Ni7 for the Comprehension of Anode Surface Chemistry of Ni‐MH Batteries

“…A noticeable feature of the resulting np‐Ni is the oriented porosity related to the stacking structure of the initial alloy. It can also be noticed that the use of a rare earth enables to obtain almost pure nickel, such as in the study of Zuo et al ., contrary to other studies (e. g. on Raney nickel), for which some aluminum remains in the produced nickel.…”

“…In the mid‐2000s, np‐Ni was intentionally developed and first obtained by electrochemical dealloying of Ni x Cu 1‐ x solid solutions, for which noble Cu first dissolves whereas Ni remains in nanoporous form. Other elements forming alloys with Ni were then investigated: Mn, Zn, Mg, Al, Fe . They dissolved in acidic media as their redox potentials are more negative than that of Ni.…”

“…They dissolved in acidic media as their redox potentials are more negative than that of Ni. Alloys can be binary or ternary compounds forming (i) solid solutions (Ni x Cu 1‐ x , NiMn, NiMnCu), (ii) intermetallics (Ni 2 Zn 11 , NiAl 4 ) (iii) bimetallic mixtures (Ni 3 Fe 7 , NiAl 3 , Ni 33 Mg 67 ), or (iv) metal glasses (MgNiY, MgNiCo). To our knowledge, there are no studies reported on the use of NiY based alloys to form np‐Ni, except that of Zuo et al .…”

“…To our knowledge, there are no studies reported on the use of NiY based alloys to form np‐Ni, except that of Zuo et al . by dealloying of amorphous Mg 90‐ x Ni x Y 10 with citric acid for supercapacitors …”

“…Consequently, CV signals are poorly defined and low scanning rates are needed to avoid voltammogram distortion due to a high ohmic drop. Zuo et al . studied the pseudocapacitive behavior of np‐Ni produced from Mg 90‐ x Ni x Y 10 .…”