Fig. 1. SEM images of Pt nanoparticle/ITO electrodes electrodeposited at various parameters. (a1?a4) Various tl (e.g. 0.01, 0.1, 1, and 2 s) at the constant of El (-0.6 V) and tu (0.1 s). (b1?b4) Various tu (e.g. 0.01, 0.1, 1, and 2 s) with the constant of El (-0.8 V vs SCE) and tl (0.1 s). The Pt loading-normalized CV curves measured at the constant of El (0.8 V) and tu (0.1 s). (c) t1 equal to 0.1 s and 1 s in 0.5 M H2SO4 solution at 0.05 V s-1. (d) t1 equal to 0.1 s and 1 s and contrast samples, which are measured in 0.1 M NH3 + 1 M KOH solution at 0.01 V s-1. (Ref. [38]).

Fig. 2. (a) Schematic illustration of shape evolution of the Pd nanocrystal and the corresponding TEM images for various morphologies, respectively (scale bars, 10 nm), where slight truncation at the corner of cubic Pd was induced by HCl oxidative etching in the early stage and then continuous atomic addition to {100} facets promotes the enlargement of {111} facets and finally results in the formation of octahedral Pd bounded by {111} facets. (b) Cyclic voltammograms of Pd nanocrystals in 0.5 M H2SO4 + 0.5 M HCOOH solution for formic acid oxidation at 50 mV s-1. (c) UV-vis absorbance for TMB oxidation after mixing with TMB for 5 min. (Reference [8]).

Fig. 3. SEM images of Pt/ITO fabricated at the different lower potential pulse duration (tl). (a?e) 1, 0.5, 0.1, 0.05 0.01 s. (f) Schematic diagram of the potentiostatic pulsed electrodeposition. CVs of the Pt/ITO electrodes with the different tl at 0.05 V s-1: (g) In 0.5 mol L-1 H2SO4 solution containing 1 mol L-1 CH3OH. (h) In N2-saturated 0.5 mol L-1 H2SO4 solution. (Ref. [12]).

Fig. 4. (a) TEM image of PtML-decorated flower-like Au particles (insert images: top right corner is the corresponding elemental mapping of Pt and Au obtained by EDS, bottom right corner is the higher magnification HAADF-STEM image of the area near the tip of the branch, revealing the surface atomic steps. (b) Cyclic voltammograms (scan rate 0.05 V s-1) of the ethanol electrooxidation on PtML-decorated spherical and flower-like Au particles in 0.5 M H2SO4 + 1 M C2H5OH. (Ref. [34]). (c) The TEM image of Pt-decorated flower-like Ni particles (the regions for A and B indexed in the right of the TEM image, and the insert image at the bottom right corner is the corresponding mapping). (d) Mass-specific activity of the ammonia electro-oxidation on Pt-decorated flower-like and featureless Ni particles obtained by different replacement reaction times of 1 and 5 min. (Ref. [16]).

Fig. 5. TEM images (insert is the corresponding mapping) of (a) dendritic core-shell PdPt bimetallic nanoparticles; (b) layered core-shell PdPt bimetallic nanoparticles; and (c) mesoporous core-shell PdPt bimetallic nanoparticles. (d) The schematic of PdPt bimetallic nanoparticles with dendritic core-shell, layered core-shell, and mesoporous core-shell structures synthesized by employing different halide ions with the same concentration of 80 mM and the corresponding TEM images (the scale bars are 20 nm). (e) CV curves of commercial Pt black (A), commercial Pt/C (B), the obtained dendritic core-shell (C, D), layered core-shell (E) and mesoporous core-shell (F) PdPt bimetallic nanoparticles synthesized by using 80 mM NaCl, HCl, NaBr and NaI, respectively. (Ref. [40]).

Fig. 6. (a) TEM image for Pt-Ir nanocubes (insert images are the size distribution). (b) The high-resolution TEM image of Pt-Ir nanocubes. CVs measured on Pt-Ir nanocubes, polycrystalline Pt-Ir NPs, and Pt nanocubes, respectively. (Reference [14]). (c) The TEM image of PdNi-HNCs-R nanoparticles. (d) High-resolution TEM, the model of nanoparticle and mapping for PdNi-HNCs-R. Cyclic voltammograms of PdNi-HNCs-R/C, PdNi-HNCs-S/C, and Pd black/C catalysts at a scan rate of 50 mV s-1 (e) In N2-saturated 1 M KOH + 1 M ethanol solution. (f) In N2-saturated 0.5 M H2SO4 + 0.5 M HCOOH solution. (Ref. [32]).

Fig. 7. (a) HRTEM of Pt-CoS2/CC. (b) EXAFS k3χ(k) oscillation functions. (c) The corresponding FT curves of CoS2/CC and Pt-CoS2/CC from Fig. 7b. (Reference [19]). (d) The TEM image of Pt/MoS2-80. (Reference [47]) (e) HAADF-STEM images of Pt/np-Co0.85Se, the area highlighted with red rectangles in regions A and B are Pt, and the right images are the STEM-EDX elemental mapping of Pt/np-Co0.85Se. (f) The normalized XANES at the Pt L3-edge of Pt foil, commercial Pt/C, PtO2, and Pt/np-Co0.85Se. The inset shows the average oxidation state of Pt in Pt/np-Co0.85Se. (Ref. [48]).

Fig. 8. (a) STEM-EDS elemental mapping of SA-Pt/WO3 hybrid. (b) Top and (c) side view of HAADF-STEM images of SA-Pt/WO3. Atomically dispersed Pt species are marked by the red circled in (b) and (c). The inset of (c) is the representative TEM image of SA-Pt/WO3; (d) H2-TPR curves of bare WO3 and Pt/WO3 hybrids. (e) Butanone response in the range of 125 ppb - 5 ppm, represents dynamic butanone oxidation sensing of SA-Pt/WO3 and measured at 150 °C. (Ref. [49]).

Fig. 9. (a?c) TEM and HRTEM images of ALD ZrO2-Pt/NCNT catalyst with 50 cycles of ALD ZrO2. (d) Schematic diagram of platinum encapsulated in zirconia nanocages structure fabricated by area-selective ALD. (e) Mass activity at 0.9 V (vs RHE) for ALD Pt/NCNT, ALD50ZrO2-Pt/NCNT600 °C, and E-TEK Pt/C catalysts. ALD Pt/NCNT and E-TEK Pt/C catalysts after 50-cycle electrochemical activation act as fresh catalysts. ALD50ZrO2-Pt/NCNT600 °C after 500-cycle electrochemical activation acts as a fresh catalyst. (Ref. [50]).

Fig. 10. (a) The formation of atomic layer Co3O4 nanofilm and cycle test of atomic layer Co3O4 nanofilm with a galvanostatic charge/discharge current density of 2 A g-1. (Ref. [60]). (b) AFM image of ultrathin Co3O4 nanosheets. (c) The Fourier transform of the EXAFS data for ultrathin Co3O4 nanosheets and commercial Co3O4 nanoparticles. (d) Discharge curves at a current density of 1.6 mA cm-3. (Ref. [58]) (e) HRTEM image and the corresponding SAED patterns of the hybrid nanosheets. (f) AFM image and the corresponding height of the hybrid nanosheets. (g) The corresponding Fourier transforms. (Ref. [64].).

Fig. 11. (a) Synthesis of ultrathin Ni2P using FGR to reduce the lattice strain during phosphorization with different precursors. (b) AFM image of NP-FG and section analysis along the line. (c) TEM image of NP-FG and the inset image is corresponding SAED pattern. (d) Photocatalytic H2 evolution with different catalysts under visible-light irradiation for 2 h. (Ref. [82]). (e) Schematic illustration of the synthetic procedures for Co9S8, Co3S4, and CoS2 HNSs, respectively. (f) Crystal structures of CoS2, Co3S4, Co9S8, CoS4 tetrahedron and CoS6 octahedron, respectively. (g) The TEM image of CoS2 HNSs. (h) Overall water splitting activity of CoS2 HNSs + CoS2 HNSs at different temperatures. (Ref. [72]).

Fig. 12. (a) TEM image of NiCo2S4/N-CNT. (b) Elemental mapping of NiCo2S4/N-CNT. (c) Comparison of OER and ORR bifunctional activity of NiCo2S4/N-CNT with representative electrocatalysts in references. The dotted lines show the △E at constant values. (d) 1 st and 150th discharge/charge curves of NiCo2S4/N-CNT electrode. (Ref. [85]).

Fig. 13. (a) The TEM image of NiCo2S4@g-C3N4-CNT. (b) Cycling performance of rechargeable ZABs with a duration of 20 min per cycle at 10 mA cm-2 for NiCo2S4@g-C3N4-CNT and Pt/C + RuO2. (c) Calculated d-band positions of metallic Ni and Co sites and (d) Free energy diagram of ORR and OER processes on bare NiCo2S4, NiCo2S4@N-GN, and NiCo2S4@g-C3N4. (Ref. [86]).

Fig. 14. (a) Preparation of the Co-NPs@NC, Co-ACs@NC, and Co-SAs@NC catalysts. (b) TEM image and (c) elemental mapping of Co-SAs@NC. (d) HAADF-STEM image of Co-SAs@NC. (Ref. [93]).

Fig. 15. (a) Protocols for the synthesis of Ni/GD and Fe/GD. A two-step strategy for anchoring-isolated Ni/Fe atoms on GD, including the in situ growth of GD layers on 3D carbon cloth (CC) surfaces via Glaser-Hay cross-coupling reaction, followed by the electrochemical reduction of metal ions (Ni2+ and Fe3+) into zerovalent metallic species [Ni(0) and Fe(0), respectively]. (b) Additional HAADF-STEM image of Ni/GD, and inset is the size distribution of Ni atoms counted from HAADF-STEM images (>560 Ni atoms considered, the most probable value is 1.23 ± 0.40 Å). Scale bar, 2 nm. (c) Additional HAADF-STEM image of Fe/GD, and insert is the size distribution of Fe atoms counted from HAADF-STEM images (>1070 Fe atoms considered, the most probable value is 1.02 ± 0.33 Å). Scale bar, 2 nm. (d) Electrostatic potential maps of pristine GD, Ni/GD, and Fe/GD, respectively. (e) The chemisorption energy of H for HER performance related to the free energy profile (ΔG). The Ni/FeC1 and Ni/FeC2 mean the H adsorption on the C1 and C2 sites within Ni/Fe-on-GD system, respectively. The GDC1 and GDC2 denote the H adsorption on pristine GD system. (Ref. [94]).