(246b) In Situ Measurement of Nanoparticle-Support Interactions in Supported Bimetallic Catalysts

Metal-support interactions (MSI) are pivotal for properties and performance of functional nanomaterials. MSI encompass a range of interactions, including chemical bonding, electrostatic forces, and van der Waals interactions, which collectively govern the adhesion of metal nanoparticles (NP) to a support. In heterogeneous catalysis, where oxide-supported metal NP play a central role, MSI control catalyst properties such as metal dispersion and catalyst stability, enhancing catalytic performance and lifetime. While a fundamental understanding of these interactions is hence essential, only a single experimental technique exists to-date that can directly measure nanoparticle adhesion, and this technique is inherently limited to monometallic systems. Multimetallic NP adhesion has so far eluded direct experimental measurement and hence remains poorly understood.

Here, we present a novel technique for the measurement of nanoparticle adhesion via “In situ measurement of Nanoparticle-Support Interactions” (INSI). The technique couples the spatial resolution of transmission electron microscopy (TEM) with the force resolution of atomic-force-microscopy (AFM), enabling direct measurement of the force of adhesion via probing in situ the formation and separation of an interface between an individual metal nanoparticle and an oxide-coated AFM probe.

We validated the technique by measuring the work of adhesion for monometallic supported nanoparticles (Pt, Pd, Au, and Ag on CeO₂, TiO₂, and MgO) and verifying the results against reported trends. We then applied the technique to three ceria-supported bimetallic nanoparticle systems (AuPt, AuPd, and AuAg; each 0 – 100% Au) and found complex, non-monotonic relationships between adhesion and composition. A simple analytical model of interfacial bonding was able to accurately reproduce the observed behavior, suggesting that adhesion between bimetallic particles and oxide supports is primarily governed by charge transfer between the constituent metals.

This new ability to probe the impact of alloying on nanoscale adhesion has the capacity to advance fundamental understanding of heterogeneous catalysis by multimetallic nanoparticles.