Pd-Ru Alloy Nanocages with a Face-Centered Cubic Structure and Their Enhanced Activity toward the Oxidation of Ethylene Glycol and Glycerol

This article reports a facile method for the synthesis of Pd-Ru nanocages by activating the galvanic replacement reaction between Pd nanocrystals and a Ru(III) precursor with I- ions. The as-synthesized nanocages feature a hollow interior, ultrathin wall of approximate to 2.5 nm in thickness, and a cubic shape. Our quantitative study suggests that the reduction rate of the Ru(III) precursor can be substantially accelerated upon the introduction of I- ions and then retarded as the ratio of I-/Ru3+ is increased. The Pd-Ru nanocages take an alloy structure, with the Ru atoms in the nanocages crystallized in a face-centered cubic structure instead of the hexagonal close-packed phase taken by bulk Ru. Using Pd nanocubes with different edge lengths, the dimensions of the nanocages in the range of 6-18 nm can readily be tuned. When tested as catalysts toward the electro-oxidation of ethylene glycol and glycerol, respectively, the Pd-Ru cubic nanocages prepared from 18 nm Pd cubes exhibit 5.1- and 6.2-fold enhancements in terms of mass activity relative to the commercial Pd/C. After 1000 cycles of accelerated durability test, the mass activities of the nanocages are still 3.3 and 3.7 times as high as that of the pristine commercial Pd/C catalyst, respectively.