Letter pubs.acs.org/NanoLett
Residual Silver Remarkably Enhances Electrocatalytic Activity and Durability of Dealloyed Gold Nanosponge Particles Guangfang Grace Li,† Ye Lin,‡ and Hui Wang*,† †
Department of Chemistry and Biochemistry and ‡Department of Chemical Engineering, University of South Carolina, Columbia, South Carolina 29208, United States S Supporting Information *
ABSTRACT: Percolation dealloying of multimetallic alloys entangles the selective dissolution of the less-noble elements with nanoscale restructuring of the more-noble components, resulting in the formation of spongelike, nanoporous architectures with a unique set of structural characteristics highly desirable for heterogeneous catalysis. Although the dealloyed nanoporous materials are compositionally dominated by the more-noble elements, they inevitably contain residual less-noble elements that cannot be completely removed through the percolation dealloying process. How to employ the lessnoble elements to rationally guide the structural evolution and optimize the catalytic performances of the dealloyed noble metal nanocatalysts still remains largely unexplored. Here, we have discovered that incorporation of Ag into Au− Cu binary alloy nanoparticles substantially enhances the Cu leaching kinetics while effectively suppressing the ligament coarsening during the nanoporosityevolving percolation dealloying of the alloy nanoparticles. The controlled coleaching of Ag and Cu from Au−Ag−Cu ternary alloy nanoparticles provides a unique way to optimize both the surface areato-mass ratios and specific activities of the dealloyed nanosponge particles for the electrocatalytic oxidation of alcohols. The residual Ag in the fully dealloyed nanosponge particles plays crucial roles in stabilizing the surface active sites and maintaining the nanoporous architectures during the electrocatalytic reactions, thereby greatly enhancing the durability of the electrocatalysts. The insights gained from this work shed light on the underlying roles of residual less-noble elements that are crucial to the rational optimization of electrocatalysis on noble-metal nanostructures. KEYWORDS: Residual less-noble elements, percolation dealloying, nanoporosity, noble-metal nanoparticles, electrocatalysis
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reactions,2,6,16 although the detailed mechanisms of such catalytic enhancements still remain ambiguous and open to further scrutiny. Despite their remarkable initial activities, the dealloyed nanoporous materials inevitably undergo activity deterioration over time during catalytic or electrocatalytic reactions due to reduced surface area-to-mass ratio and loss of surface active sites, both of which are caused by the thermodynamically driven ligament coarsening.15,17,18 While it was recently observed by in situ environmental electron microscopy that residual Ag could locally stabilize the surface atomic steps (active sites) during catalytic CO oxidation,4 how to rationally incorporate residual Ag into the Au nanoligaments to optimize both the catalytic activity and durability of the dealloyed materials still remains an open question. Here, we show that incorporating Ag into Au−Cu binary alloy NPs not only substantially accelerates Cu leaching but also effectively suppresses ligament coarsening during nanoporosity-evolving percolation dealloying, which provides a unique way to optimize both the surface area-to-mass ratios
ealloying of alloys involves intriguing nanoscale structureremodeling processes that profoundly influence the catalytic properties of the dealloyed materials.1,2 This is best manifested by the percolation dealloying of Au−Ag alloy membranes, which results in nanoporous foams consisting of Au-rich nanoligaments that are interconnected to form a unique 3D solid−void bicontinuous, spongelike architecture.2−5 Distinct from the catalytically inert bulk Au membranes, the dealloyed nanoporous Au foams exhibit superior catalytic activities commensurate with those of oxide-supported ultrasmall Au nanocatalysts (
