Facile Synthesis of Pd–Pt Alloy Nanocages and Their Enhanced Performance for Preferential Oxidation of CO in Excess Hydrogen

This article describes a new method for the facile synthesis of Pd–Pt alloy nanocages with hollow interiors and porous walls by using Pd nanocubes as sacrificial templates. Differing from our previous work (Zhang, H.; Jin, M. S.; Wang, J. G.; Li, W. Y.; Camargo, P. H. C.; Kim, M. J.; Yang, D. R.; Xie, Z. X.; Xia, Y. Synthesis of Pd-Pt Bimetallic Nanocrystals with a Concave Structure through a Bromide-Induced Galvanic Replacement Reaction. J. Am. Chem. Soc.2011, 133, 6078–6079), we complemented the galvanic replacement (between Pd nanocubes and PtCl42–) with a coreduction process (for PdCl42– from the galvanic reaction and PtCl42– from the feeding) to generate Pd–Pt alloy nanocages in one step. We found that the rate of galvanic replacement (as determined by the concentrations of Br– and PtCl42– and temperature) and the rates of coreduction (as determined by the type of reductant and temperature) played important roles in controlling the morphology of resultant Pd–Pt alloy nanocages. The Pd–Pt nanocages exhibited both enhanced activity and selectivity for the preferential oxidation (PROX) of CO in excess hydrogen than those of Pd nanocubes and the commercial Pt/C thanks to the alloy composition and hollow structure. In addition, as the sizes of the Pd–Pt nanocages decreased, they exhibited higher CO conversion rates and lower maximum conversion temperatures due to the increase in specific surface area.