Convergent Galvanic Replacements for Carbon-Supported Silver–Palladium–Platinum Nanoalloys as Multifunctional Electrocatalysts

Galvanic replacement reaction (GRR), which arises from the difference in redox potential between two metal species in different oxidation states, is a powerful tool for designing structures with unique functionalities. However, extending GRR to more than two metals to target homogeneous structures remains puzzling. Here, we interrogated a single-step, low-temperature, convergent GRR strategy for assessing silver–platinum-palladium materials with tunable physicochemical and electrocatalytic properties. We synthesized carbon-supported silver (Ag/C, 19 wt %) using a solid-state carbo-reduction method. Then, silver atoms within Ag/C were engaged in GRRs with Pt(II)–Pd(II) species within a brine solution. Although thermodynamically favorable, the GRR between Ag(0) and Pt(II) requires a larger molar excess of Pt(II) than that between Ag(0) and Pd(II). We postulate that, in the presence of both metal precursors, the mechanisms of preferential replacement of silver atoms at the center of the particle by Pt(II) and homogeneous replacement by Pd(II) converge to produce porous architectures. Extensive characterization combined with glycerol electrooxidation and the oxygen reduction reaction (ORR) reveals the potential to drastically tune the electrocatalytic properties of the resulting materials by adjusting their electronic properties based on the amounts of Pt and Pd that enter and Ag that leaves the initial structure. This yields a low-loading trimetallic Ag/C_GRR-Pt+Pd electrocatalyst (3–9 wt % Pt+Pd) whose catalytic activity toward glycerol electrooxidation is twice that of bimetallics (Ag/C_GRR-Pt and Ag/C_GRR-Pd) and five to ten times that of state-of-the-art Pt/C and Pd/C electrocatalysts. The present knowledge could stimulate the exploration of complex GRR processes for designing medium- to high-entropy materials.