Decoupling Strain and Ligand Effects in Ternary Nanoparticles for Improved ORR Electrocatalysis

Density functional theory is used to investigate OH adsorption on ternary Pt-Au-M (M = 3d-metal) nanoparticles in order to address their potential to improve activity for the oxygen reduction reaction (ORR) compared to pure Pt nanoparticles. The nanoparticles are investigated through a method developed for decoupling strain and ligand effects and then correlated with the extended Pt(111) surface for benchmarking. Subsurface Au has previously been shown to form a passivating layer, stabilising the nanoparticle catalysts against the harsh acidic conditions at the cathode, while the current study shows the effect of the ternary metal core allowing for tuning the catalytic activity through strain effects. Good agreement is found with experimental studies showing increased activity of Pt-Au-Fe/Ni nanoparticles, and the current study suggests that mid to late 3d-metals should also exhibit enhance activity and stability with respect to pure Pt nanoparticles. It is suggested that the Pt-Au-M for M = Cr, Mn, Co, Cu, Zn nanoparticles are of particular interest as they exhibit an optimal interplay between strain, ligand effects and stability.