Electrical charge-induced selective ion permeation in HfO2/porous nickel silicide hierarchical structuresElectronic supplementary information (ESI) available: SEM images of Au NP arrays obtained under optimally annealed conditions; heating profile for the formation of the NiSi conductive phase; calibration of electrolyte conductivity versus salt concentration; flexural strength of porous NiSi and AAO membrane by three-point flexural testing. See DOI: 10.1039/c5ra03278d

HfO 2 /porous nickel silicide (NiSi) hierarchical structures fabricated by metal-assisted chemical etching (MACE) followed by a silicidation process and deposition of HfO 2 by atomic layer deposition (ALD) have been. The as-formed porous structures are systematically investigated using etching solutions of various HF/H 2 O 2 ratios and the manipulation of electrical double-layer (EDL) overlapping, leading to electrical charge-induced selective ion penetration in HfO 2 /porous NiSi hierarchical structures. Its desalination ability was examined, in which the ionic concentration of saline water can be reduced by 21% when a bias of 2 V was applied. In addition, the mechanical property of the as-formed porous NiSi membrane was estimated to have a flexural strength of 124.04 MPa. These porous NiSi membranes can be continuously operated for 18 h without loss of its deionization ability. HfO 2 /porous nickel silicide (NiSi) hierarchical structures fabricated by metal-assisted chemical etching (MACE) followed by a silicidation process and deposition of HfO 2 by atomic layer deposition (ALD) have been demonstrated.