Bimetallic Ag-Au nanoparticles from nanoconfinement: adjusting properties by electrochemical synthesis

Developing synthetic pathways that exhibit well-controlled yet versatile characteristics to prepare nanoparticles (NPs) with properties tailored to the desired application is a topic of continuous interest. Herein, we introduce an innovative approach to form bimetallic alloy and core–shell-like Ag–Au NPs, employing reverse micelles as nanoreactors at the polarized electrolyte/electrode interface. Encapsulation of the metal precursors in the nanocavities of polystyrene-b-poly(2-vinylpyridine) (PS–P2VP) reverse micelles provides a route to control the NP size without the need for additional chemicals. By investigating the relations between the electrochemical driving force of the process and the complex interplay among the precursor species and the electrolyte medium, bimetallic Ag–Au NPs with sizes ranging from below 10 nm to 140 nm were synthesized with adjustable element configuration (core–shell vs. alloy) and composition. Notably, the resultant NPs were either Ag-rich alloys or Au-rich alloys or had a core–shell-like configuration with adjustable core and shell compositions based on the applied electrode potential and electrolyte medium. Finally, the prepared NPs were evaluated for their catalytic activity based on their physical properties against the hydrogen evolution reaction, where the core-shell-like NPs showed the most promising performance.