Urea hydrogen bond donor-mediated synthesis of high-index faceted platinum concave nanocubes grown on multi-walled carbon nanotubes and their enhanced electrocatalytic activity.

We have reported, for the first time, in situ growth of high-index {hk0} faceted concave Pt nanocubes on multi-walled carbon nanotubes (CNTs) via an electrochemical method in choline chloride-urea (ChCl-U) based deep eutectic solvents (DESs). Mechanistic studies indicate that a urea hydrogen bond donor (HBD) plays a key role in the formation of concave Pt nanocubes, in which the urea HBD preferentially adsorbs onto the {100} faces and blocks the growth of nanocrystals along the 〈100〉 axis. The as-prepared concave Pt nanocubes are characterized to be enclosed mainly with high-index {710}, {610} and {510} facets. It has been determined that the concave cubic Pt/CNT exhibits higher catalytic activity and stability than the flower-like Pt/CNT and commercial Pt/C catalysts, and this is ascribed to its high density of surface atomic steps and the synergistic effect between the CNT and Pt nanocubes.

Identification of a quasi-liquid phase at solid-liquid interface.

An understanding of solid-liquid interfaces is of great importance for fundamental research as well as industrial applications. However, it has been very challenging to directly image solid-liquid interfaces with high resolution, thus their structure and properties are often unknown. Here, we report a quasi-liquid phase between metal (In, Sn) nanoparticle surfaces and an aqueous solution observed using liquid cell transmission electron microscopy. Our real-time high-resolution imaging reveals a thin layer of liquid-like materials at the interfaces with the frequent appearance of small In nanoclusters. Such a quasi-liquid phase serves as an intermediate for the mass transport from the metal nanoparticle to the liquid. Density functional theory-molecular dynamics simulations demonstrate that the positive charges of In ions greatly contribute to the stabilization of the quasi-liquid phase on the metal surface.

Excavated cubic platinum-iridium alloy nanocrystals with high-index facets as highly efficient electrocatalysts in N2 fixation to NH3.

Excavated cubic Pt93Ir7 alloy nanocrystals enclosed by high-index {710} facets exhibit excellent electrocatalytic properties for the nitrogen reduction reaction (NRR) with a high faradaic efficiency (40.8%) and NH3 production rate (28 µg h-1 cm-2). The presence of Ir on the Pt stepped surface suppresses the hydrogen evolution reaction (HER) and accelerates the NRR.