No abstract

A facile synthesis strategy has been developed to synthesize palladium nanocubes with tunable size and well-controlled morphology. Through adjusting the dosages of acetate species (KOAc, NHOAc, and HOAc), the sizes of well-defined Pd nanocubes are tuned. The reduction of Pd precursors, a first-order reaction, is influenceable by acetate species, and a quantitative relationship between cubic width and apparent reduction rate constant, which has been found to be an effective parameter to describe the growth process of Pd nanocubes, has been uncovered. The effect of apparent reduction rate constant on the growth of Pd nanocubes has been discussed, and the growth kinetics of Pd nanocubes is quantitatively depicted.

In this work, the growth pattern of size controllable Pd nanocubes is studied systematically under a variety of reaction conditions.

The catalytic properties of Pt-based alloy nanocrystals are highly dependent on their morphologies, particle sizes, and compositions, but it remains a grand challenge to obtain well-controlled nanocrystals. Herein, we report a facile but efficient synthetic strategy for the size-controlled synthesis of AgPt and AgPtAu nanoparticles. By subtle variation of initial reduction kinetics in a modified polyol method, AgPt octahedra with tunable sizes from 4.0 to 13.5 nm have been synthesized. On the basis of size-controlled AgPt seeds, AgPtAu nanoparticles with different sizes and compositions were prepared by subsequent introduction of Au. For the AgPt series, the smallest AgPt octahedra showed the highest mass activity but the poorest durability for the formic acid oxidation reaction (FAOR). Furthermore, the introduction of Au into AgPt nanoparticles brought about tremendous influences in the size- and composition-relevant electrochemical properties. The medium-sized AgPtAu with appropriate Au contents, e.g., Au28% ∼ 13.5 nm, exhibited a mass activity of 2101 mA mg–1 for the FAOR in the favored direct oxidation pathway, which was about 11.2-fold that of commercial Pt. As the electrocatalytic properties of AgPtAu displayed little decay in the accelerated durability tests of 30 000 cycles, the highly active AgPtAu octahedra showed great potentials as promising electrocatalysts for the FAOR.

The functions of heterogeneous metallic nanocrystals (HMNCs) can be undoubtedly tuned by controlling their morphologies and compositions. As a less-studied kind of HMNCs, corner-satellite multi-metallic nanocrystals (CSMNCs) have great research value in structure-related electrocatalytic performance. In this work, PdAgPt corner-satellite nanocrystals with well-controlled morphologies and compositions have been developed by temperature regulation of a seed-mediated growth process. Through the seed-mediated growth, the morphology of PdAgPt products evolves from Pd@Ag cubes to PdAgPt corner-satellite cubes, and eventually to truncated hollow octahedra, as a result of the expansion of {111} facets in AgPt satellites. The growth of AgPt satellites exclusively on the corners of central cubes is realized with the joint help of Ag shell and moderate bromide, and hollow structures form only at higher reaction temperatures on account of galvanic displacement promoted by the Pd core. In view of the different performances of Pd and Pt toward formic acid oxidation (FAO), this structure-sensitive reaction is chosen to measure electrocatalytic properties of PdAgPt HMNCs. It is proven that PdAgPt CSMNCs display greatly improved activity toward FAO in direct oxidation pathway. In addition, with the help of AgPt heterogeneous shells, all PdAgPt HMNCs exhibit better durability than Pd cubes and commercial Pt.