Design Principles of Heteroepitaxial Bimetallic Catalysts

Abstract

Heteroepitaxial bimetallic catalytic materials have been attracting considerable interest because of their unique properties and applications in energy, chemicals, and fuel sectors. Optimizing the activity of bimetallic catalysts requires the ability to understand and precisely manipulate the nanostructure (loading and dispersion of an admetal on a host metal). Ammonia decomposition catalyzed by Ni on Pt(111) [Ni/Pt(111)] is a prototype structure sensitive reaction for this purpose, in which both N–H bond breaking and N–N bond formation can be rate-limiting steps. Here, a first-principles kinetic Monte Carlo simulation framework reveals the bifunctional role of Ni clusters on Pt(111) in NH3 decomposition: dehydrogenation on Ni terrace and N2 desorption near Ni steps on Pt. We show that the dynamic interplay between surface nitrogen diffusion and association near the steps of Ni clusters and Pt terraces is responsible for the lower than expected nitrogen desorption temperature found in experiments. Our res...