Electrochemical synthesis of multimetallic nanoparticles and their application in alkaline oxygen reduction catalysis

Conventional solvothermal synthesis of nanoparticles relies on the metal-ligand chemistry in the control of size and exposed facets. Because the surfaces of the nanoparticles are typically covered with surfactant molecules, these synthetic nanoparticles are often ineffective catalysts for chemical transformations. Moreover, recent applications of nanoparticles as electrocatalysts require costly processes, such as calcination or potential cycling, when converting the nanoparticles to electrodes. Here, we report a novel electrochemical route in direct synthesis of surfactant-free multimetallic nanoparticles. The synthesis occurs by electrolysis of an aqueous nanodroplet (approximately 50 attoliter in volume) containing metal precursor ions, and the stoichiometry inside the nanodroplet precisely translates to the synthesized nanoparticle. Multimetallic nanoparticles of binary, ternary, and quaternary combinations are prepared employing Cu, Ag, Pd, Pt, and Au as constituents. The synthesized nanoparticles are evaluated as electrocatalysts for alkaline oxygen reduction. Particularly, Cu_0.75Pd_0.25 and Cu_0.375Pd_0.25Pt_0.375 nanoparticles demonstrate catalytic performance comparable to the benchmark catalyst Pt/C and boast far superior durability, while consuming at least 200 fold less metal atoms.