Theoretical design of platinum-sliver single atom alloy catalysts with CO adsorbate-induced surface structures

In this work, by combining density functional theory calculations and Monte Carlo simulations with cluster expansion Hamiltonian methods, we investigate the surface aggregation of Pt atoms on the Pt/Ag(111) surface under vacuum conditions and in the presence of CO. The results show the decisive influence of CO-CO interactions and reveal the competition between CO-metal interactions and CO-CO repulsion. Thus, in addition to evidence of reverse Pt segregation caused by CO adsorption, two methods for tuning the surface Pt atomic system synthesis are found, where the surface can be adjusted by tuning the CO coverage to obtain a larger number of monomers (0.25 ML CO coverage) or a pure Pt layer (1 ML coverage) at Pt bulk concentrations above 10%. For highly dilute alloys, the Pt distribution can be controlled by adjusting the concentration. Indeed, for a Pt bulk concentration close to 8% and a CO coverage of about less than 1 ML, between 400 and 600 K, an ordered structure has been observed which maximized the number of Pt monomers and homogeneous distribution on the surface. The overpotential (eta) of the ordered Pt3Ag(111) surface is 0.41 V, slightly lower than that of pure Pt(111) (eta = 0.43 V), indicating a potential candidate for ORR catalysts with rich active sites and a low overpotential.

Automated summary

This study investigates the surface aggregation of Pt atoms on the Pt/Ag(111) surface under different conditions using density functional theory calculations and Monte Carlo simulations. The results reveal the decisive influence of CO-CO interactions and the competition between CO-metal interactions and CO-CO repulsion. Two methods for synthesizing the surface Pt atomic system are found, and the Pt distribution can be controlled by adjusting the concentration. An ordered structure with the maximized number of Pt monomers and homogeneous distribution on the surface is observed. The ordered Pt3Ag(111) surface shows a lower overpotential compared to pure Pt(111), suggesting its potential as a candidate for ORR catalysts with rich active sites and a low overpotential.