Unravelling Surface Composition of Bimetallic Nanoparticles

Abstract Accurately determining the surface composition of bimetallic nanoparticles (bi‐MNPs) is crucial in assessing their catalytic potential for energy applications and surface‐enhanced Raman scattering (SERS). Despite its importance, characterizing the surface composition of bi‐MNPs is still extremely difficult with existing techniques. Here, we show that the challenge is approached by combining extended X‐ray absorption fine structure (EXAFS) analyses and modeling calculations. A generally applicable methodology using an ethylene glycol‐assisted redox transmetallation (EG‐RTM) strategy has been used to deduce the surface Pt composition of various Pt–Ru bi‐MNPs to facilitate discussion of their electrochemical catalytic efficiency. Further discussion is focused on SERS, related to the surface Ag content of various Ag–Pt bi‐MNPs formed in ethylene glycol solutions at controlled pH values. Although the present methodology is demonstrated on fcc structured bi‐MNPs it should be transferable to bi‐MNP structures with different shapes and also to ternary nanoparticles. The proposed methodology enables us to deduce the surface composition of bi‐MNPs from experimental data directly and to estimate the surface composition under real conditions, when compared to simulation. The ability of the present combined modeling and experimental approach makes it a unique tool in our quest to understand the physical and chemical properties of NPs.