Characterization of Nanowire-Constructed Porous CuZn and CuNiZn Nitrate-Active Electrodes Prepared via Galvanic Displacement on Electrodeposited Zn Templates in Ionic Liquids

Nanowire-constructed porous CuZn and CuNiZn electrodes were prepared through galvanic displacement on electrodeposited tangled Zn nanowires in ionic liquids (ILs). The sacrificial templates of tangled Zn nanowires were potentiostatically electrodeposited from amide-type IL 1-butyl-1-methylpyrrolidinium bis ((trifluoromethyl)sulfonyl)amide ([BMP][TFSA]) containing ZnCl 2 as the Zn(II) precursor as long as an appropriate potential was applied. Another amide-type IL tributylmethylammonium bis ((trifluoromethyl)sulfonyl)amide ([Bu 3 MeN][TFSA]), which is much more viscous than [BMP][TFSA], was used as the medium for the galvanic displacement reaction between Zn and Cu(II)/Ni(II). A more viscous medium was used for the sake of slowing the displacement rate by reducing the mass transport; otherwise, the nanowire structure could not be preserved after the galvanic displacement. The concentration of chloride (Cl − ) in the ILs, which determines the reduction potentials of the chloro-coordinated Cu(II) species, also shows a crucial effect on the displacement rate that is also controlled by the separation of reduction potential between Zn and Cu. Both porous CuZn and CuNiZn electrodes showed activity towards the reduction of nitrate (NO 3 − ) in aqueous 0.1 M NaOH. CuNiZn prepared with a displacement time of 90 min showed superior current density despite the electrode surface area determined by geometry (disk electrode) or double-layer capacitance, indicating that the introduction of Ni probably improved the unit activity of the active sites in addition to the enlargement of active surface area. Graphical Abstract