Engineering Chemical\nand Catalytic Activity of Metal\nSurface Sites by Controlling Strain and Ligand Effects in Nonmodel\nNanoparticle Catalysts

Binding energy of reactants on heterogeneous catalyst\nsurface sites\nis a well-established catalytic activity descriptor for many chemical\nreactions. However, systematically manipulating the binding energies\nby engineering the catalytic surface sites has proven challenging.\nHerein, we propose a nanoparticle catalyst structure that contains\nan alloy core composed of miscible metal atoms, surrounded by layers\nof a different material, and covered by a layer of catalytically active\nmetal. The alloy core controls the lattice strain of the nanoparticle\nand therefore the distance between the surface atoms, while the subsurface\nlayer atoms induce a ligand effect on the surface atoms. We show that\nthis class of materials allows us to systematically control the adsorbate\nbinding energies with high precision. We illustrate our findings by\ndeveloping nonmodel nanoparticle catalysts that employ an AuCu alloy\nwith controlled composition as the core, Au as the surrounding layers,\nand Pt as the active surface metal. Electrochemical CO stripping measurements\nsuggest that the CO binding energy on the surface Pt sites can be\nsystematically tuned by varying the composition of the alloy core.\nOur analysis suggests that the change in the CO binding energy of\nPt is the result of the combined ligand effect from the Au layers\nand strain effect from the AuCu core. The presented catalyst structure\nallows for precise modulation of the strain and ligand effect for\ntuning the local chemical environment of any catalytic materials,\nwhich may aid the development of next-generation catalysts.