Unveiling the Influence of Inherent Parameters of AgPt and AgPtAu Octahedra upon Formic Acid Electrooxidation

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.