Surface-Limited Galvanic Replacement Reactions of Pd, Pt, and Au onto Ag Core Nanoparticles through Redox Potential Tuning

Galvanic replacement reactions (GRR) have served as a powerful synthetic strategy to obtain hollow and morphologically complex bimetallic nanostructures. Extensive work has been done in the literature to vary the synthetic parameters of GRR, but achieving a surface self-limiting galvanic exchange remains challenging. In this work, we tune the extent of GRR between Ag0 nanoparticles and Pd, Pt, and Au ions through tailored complexation of metal cations with organic amine and phosphine ligands. Increasing the number of bound organic ligands systematically lowers the reduction potential of the metal ion and therefore the driving force toward GRR with Ag0. In each case, we are able to obtain an oxidized metal–ligand complex with a sufficiently low GRR driving force to restrict metal deposition to the surface of the Ag core. This synthetic method serves as a general strategy to synthesize bimetallic Ag@AgM or Ag@M (M = Pd, Pt, Au) core-shell nanoparticles and may be extendable to other galvanic replacement reactions of base metal cores with noble metal complexes. By depositing the Pt and Pd atoms only at the surface of the nanoparticle, these materials exhibit good mass-activity in the electrocatalytic hydrogen evolution reaction.