Fig. 1 Schematic of NP materials for energy storage, sensors and electrocatalysts

Fig. 2 a XRD pattern, b cross-sectional (scanning electron microscopy) SEM image, c TEM image, d high-resolution transmission electron microscopy (HRTEM) image of the resultant NP Ag by dealloying the Ag45Mg35Ca20 metallic glass in 0.05 mol L−1 HCl aqueous solution for 4 h at room temperature. Reprinted with permission from [39]

Fig. 3 Surface morphologies of the resultant NP silver by dealloying the Ag45Mg35Ca20 MG at room temperature in a 0.025 mol L−1 HCl solution for 8 h, b 0.1 mol L−1 HCl solution for 2 h, c 1 mol L−1 HCl solution for 1 h, d 12 mol L−1 HCl solution for 10 min, respectively. Reprinted with permission from [39]

Fig. 4 a XRD pattern of the NP Cu thin film fabricated by chemical dealloying in 0.005 mol L−1 HF solution for 24 h, and the inset is the corresponding XPS spectra of Cu-2p. b Cross-sectional image of the NP Cu thin film. c TEM, d HRTEM images of the ligaments of the NP Cu thin film, respectively. Reprinted with permission from [38]

Fig. 5 Characterization of NP Ni/MG. a SEM image of the cross section of the dealloyed NP Ni/MG wire. b, c, d Surface morphologies of the dealloyed Ni40Zr40Ti20 MG wire. Reprinted with permission from [40]

Fig. 6 Morphology of the porous alloy. a and b SEM images of the residual alloy (panel b is highly magnified). The speed of the copper roller is 4 K rpm. The pore sizes were tuned by the cooling rate and characterized by the speed of the copper roller: c 2 K, d 1 K, e 500 rpm. f Variation in the pore size and specific surface area (SSA) with the rotation rates of the copper roller. Scale bars are 500 nm for panel a, 100 nm for panel b, and 1 μm for panels c-e. Reprinted with permission from [44]

Fig. 7 Surface morphologies of the Ag NPs produced by chemical dealloying in a 0.025 mol L−1 HCl aqueous solution for a 2 h, b 6 h, c 8 h, d 12 h, e 24 h, f 36 h at room temperature. Reprinted with permission from [39]

Fig. 8 Microstructures of the resultant NP Ag by dealloying the Ag45Mg35Ca20 MG in the 0.05 mol L−1 HCl solution for 4 h at different temperatures: a 273 K, b 298 K, c 323 K, d 348 K, e 368 K. The insets in each image show the corresponding cross section of the NP silver. Reprinted with permission from [39]

Fig. 9 a Dependence of ligament size on dealloying time at different temperatures. b Plot of lnd vs lnt at each dealloying temperature for deriving the coarsening exponent. c Plot of ln (dn/t) vs (RT)−1 for deriving the activation energy. Reprinted with permission from [39]

Fig. 10 SEM images of the as-dealloyed samples. a Cu50Zr45Al5, b Cu50Zr43Al5Ag2, c Cu50Zr40Al5Ag5, d Cu50Zr38Al5Ag7, e Cu50Zr35Al5Ag10. f Variation in the surface area and pore size as a function of Ag. Reprinted with permission from [31]

Fig. 11 a XRD patterns of the as-spun and as-dealloyed Cu50Zr33Al5Ag12, b SEM images of the NP Cu-Ag fabricated by dealloying Cu50Zr33Al5Ag12 MG in the 0.01 mol L−1 HF aqueous solution at room temperature for 40 h. Reprinted with permission from [31]

Fig. 12 Schematic illustration of the dealloying mechanism in the Cu-Zr-Al-Ag MGs. a Amorphous precursor, b dissolution of Zr and Al atoms, agglomeration of Cu and Ag into tiny clusters, c formation of porous structures. The red circle in b2 illustrates the mutually exclusive process between the Cu and Ag atoms. Reprinted with permission from [31]

Fig. 13 a Surface morphology of the dealloyed Ni40Zr40Ti20 MG ribbon. b Surface morphology of the dealloyed Ni40Zr40Ti17Pt3 MG ribbon. Reprinted with permission from [55]

Fig. 14 a Digital photograph of a primitive Cu60Zr35Al5 glassy precursor, a dealloyed NP Cu sample and the sample covered with the Cu(OH)2 nanograss structure (left to right). b SEM image of an as-prepared free-standing nanohybrid. c Surface morphology of the Cu(OH)2 nanograss@NP Cu hybrid. The inset shows an enlarged SEM image of the Cu(OH)2 nanograsses. d Cross section of the nanohybrid. Reprinted with permission from [56]

Fig. 15 a Cross-sectional morphology and energy-dispersive spectroscopy (EDS) analysis (inset) of the dealloyed NP Cu. b Surface morphology of the NP Cu. c Overall SEM image of the free-standing CuO nanocomposite. The inset shows the cross-sectional image of the nanocomposite. d Surface morphology of the as-prepared CuO nanocomposite. Reprinted with permission from [57]

Fig. 16 Schematic of the fabrication process for the NP Ag/MnO2 composite by electroless plating of MnO2 into the NP Ag nanopores. a Surface SEM image of NP Ag before plating. b Surface SEM image of NP Ag after plating. Reprinted with permission from [58]

Fig. 17 Schematic illustration of the preparation of the NiCoP/NP Cu nanocomposite. Reprinted with permission from [59]

Fig. 18 a 3D reconstruction of the cross section of NP Ag by focused ion beam nanotomography. b Raman spectra without any substrate and NP silver substrate at 10-4 mol L−1 R6G. Reprinted with permission from [72]

Fig. 19 Raman spectra of the as-dealloyed Cu50Zr45-xAl5Agx (x = 0, 2, 5, 7, 10 and 12 at.%) ribbons in a 10-4 mol L−1 R6G solution. Reprinted with permission from [31]

Fig. 20 a SEM image of the NP Ag before plating. b SEM image of the NP Ag after plating. c CV curves for the NP Ag/MnO2 composite electrodes prepared with different plating times (0-30 min) and a scan rate of 100 mV s−1. d The specific capacitance changed as a function of cycle number for the NP Ag/MnO2 composite electrode plated for 20 min, and the surface morphology of the composite electrode after 1000 cycles (the inset). Reprinted with permission from [58]

Fig. 21 a SEM image of NiO/NP Ni/MG. b CV curves of the samples dealloyed for 30, 45 and 60 min measured at a scan rate of 10 mV s−1. c Charge/discharge curves of the sample immersed in 0.5 mol L−1 HF solution for 60 min at 298 K. d Volume capacitance as a function of cycle number at a sweep rate of 20 mV s−1 in 1 mol L−1 KOH solution. Reprinted with permission from [90]

Fig. 22 a SEM image of NP CuOAg. b High-magnitude SEM image. c CV figures of the NP CuOAg electrode at different scan rates. d Galvanostatic charge/discharge curves of the NP CuOAg electrode at different current densities. Reprinted with permission from [93]

Fig. 23 a Polarization curves and b Tafel plots of NP Ni/MG wire and NP Ni/MG ribbon for HER with iR compensation in 1 mol L−1 KOH. Reprinted with permission from [40]

Fig. 24 Theoretical calculations. a Atomic configuration of the Pt75Ni25 (Pt-top) model and the adsorption site of H*. b Calculated free-energy changes in different models. c Water adsorption energies for the Ni hcp, Pt top and Pt75Ni25 (Pt-top) models. Reprinted with permission from [55]

Fig. 25 Structural characterization of the core-shell-structured NP Cu@(Ni/NiO)/MGs. a Bright-field TEM image of NP Cu25Ni25. The inset shows the SAED pattern. b HRTEM images of NP Cu25Ni25. c-g High-angle annular dark field-STEM images of NP Cu25Ni25 and the corresponding EDS elemental maps. h, i HRTEM image of NP Cu25Ni25 and strain distribution of exx. (The compressive strain is represented by the color from green to dark blue, while the tensile strain is represented by the color from red to bright yellow.) [110]

Fig. 26 a TEM image of the amorphous matrix and the porous surface layer with the diameter of the nanoligaments and nanopores of approximately 10 nm. The SAED diffraction rings of the porous layer confirm the nanocrystalline structure, and the SAED pattern of the matrix shows a typical characteristic of amorphous phases with a diffraction halo. b High-angle annular dark field (HAADF) image and EDS map confirming the dissolution of Al during the reaction and the formation of Au ligaments with uniformly distributed Co, Ni, Mn and Y. c Polarization curves measured at a scan rate of 5 mV s−1. d Tafel plots for the Al85Ni7Y8, Al97Au3, Al80Ni6Co3Mn3Y5Au3 and Pt/C electrodes derived from the HER polarization curves. Reprinted with permission from [114]

Fig. 27 a Schematic illustration of the preparation process of the nanosponge-like high-entropy metallic glasses (HEMGs). b SEM and c 3D AFM images of the dealloyed HEMG ribbon surface. d Polarization curves of the as-spun and dealloyed HEMGs in 1 mol L−1 KOH solution. e Comparison of HER activities with recently reported electrocatalysts in 1 mol L−1 KOH solution [115]

Fig. 28 Structure and formation mechanism of the atom-stepped interfaces. a HR-TEM image of the as-spun Fe40Ni40B20 MG composite with in situ-precipitated FeNi3 nanocrystals. b HAADF-STEM image and the fast Fourier transformation patterns of the selected areas (the insets) of the FeNi3 nanocrystal. c Atomic structure of the stepped interface between the twinned FeNi3 nanocrystal and MG matrix. d Schematic illustration of the formation process of the stepped interface architecture during the rapid solidification. e OER polarization curves of the as-spun monolithic Fe40Ni40B20 MG, FeNi3 nanocrystal/MG composite, and commercial IrO2 and RuO2 catalysts in 1 mol L−1 KOH electrolyte. The inset shows the corresponding Tafel plots of these catalysts. f Comparison of the OER activity of the as-spun FeNi3 nanocrystal/MG composite with various recently reported state-of-the-art transition metal-based electrocatalysts in alkaline. g Mass activities of the catalysts at an overpotential of 300 mV. Error bars represent the standard deviation from five independent measurements. h Chrono-potentiometric curves were recorded at 10, 100 and 500 mA cm−2 for the composite catalyst. The inset shows the atomic structure of the stepped interface after 120 h at the high current density of 500 mA cm−2 and the electron energy loss spectroscopy elemental mapping of the selected area. [120]