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On the basis of the Gibbs free energy (GFE) model of Janus, core−shell, and alloyed structures of Ag−Cu and Ag−Au nanoparticles, the structural stability and size-composition phase diagram are obtained. For phase segregated structure, small size and low temperature are more beneficial at fixed composition. If the temperature is fixed, the segregated phase is favored at small size and low composition. The lowest critical size to phase segregation is 6 nm for Ag−Cu NPs and 4.5 nm for Ag−Au NPs at 400 K and Ag atom fraction of approximately 50%, and raising the temperature reduces the critical size. For Ag−Cu phase diagram, it is found that the core size is dominated by the transformation between Janus and core−shell structure. When the core is sufficient large, the Ag−Cu NPs will keep the core−shell structure. As the core size gets smaller, the core location will be moved from center to off-center until it forms quasi-Janus or Janus NPs. However, for the Ag−Au phase diagram, there is no Janus structure at large scale of composition.

It is a great challenge to develop highly active oxygen evolution reaction (OER) electrocatalysts with superior durability. In this study, a NiFe layered double hydroxidedecorated phosphide (NiFe LDH@CoP/NiP 3 ) was constructed to display satisfactory OER activity and good stability for water splitting in alkaline media. At an overpotential of 300 mV, NiFe LDH@CoP/NiP 3 achieved a current density of 82 mA cm −2 for the OER, which was 9.1 and 2.3 times that of CoP/NiP 3 and NiFe LDH, respectively. Moreover, the reconstruction behavior, during which oxyhydroxides formed, was studied by a combination of X-ray photoelectron spectroscopy, Raman spectroscopy, and scanning electron microscopy. A synergistic effect between NiFe LDH and CoP/NiP 3 was also observed for the hydrogen evolution reaction. Furthermore, when NiFe LDH@CoP/NiP 3 acted as both the cathode and anode for overall water splitting, a high current density of 100 mA cm −2 was maintained for more than 275 h.In addition, under Xe light irradiation, a solar-to-hydrogen efficiency of 9.89% was achieved for solar-driven water splitting. This work presents the coupling of different active compositions, and can provide a reference for designing bifunctional electrocatalysts.

Ultrasmall nanoparticles, with sizes in the 1–3 nm range, exhibit unique properties distinct from those of free molecules and larger-sized nanoparticles. Demonstrating that the hydrothermal method can serve as a facile method for the synthesis of platinum nanoparticles, we successfully synthesized ultrasmall Pt nanoparticles with an average size of 2.45 nm, with the aid of poly(vinyl pyrrolidone) (PVP) as reducing agents and capping agents. Because of the size effect, these ultrasmall Pt nanoparticles exhibit a high activity toward the methanol oxidation reaction.

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