Boron atom incorporation into metal nanoparticles

Abstract

Boron can become unintentionally incorporated into transition metals during the reduction of metal salts with borohydride. The presence of boron at the surfaces of transition metals (TMs) such as Pd and Pt is known to significantly influence their catalytic properties. In this study, we employ density functional (DFT) calculations to investigate the thermodynamics and kinetics of boron incorporation into ∼1.5 nm particles and extended (111) surfaces of fcc-Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, and Al. Our results reveal that boron exhibits high thermodynamic stability in interstitial subsurface sites on (111) surfaces and nanoparticles of Rh, Pt, and Pd. Unlike extended surfaces, metal nanoparticles (NPs) can also stabilize boron within the coordination environment of surface metal atoms, with such sites being particularly stable in Rh, Ir, and Ni nanoparticles. Furthermore, the energy barriers for B migration at NP edge sites from the surface to subsurface decrease to <0.5 eV (for all metals except Ir), and the migration barrier for boron incorporation into the in-surface sites is lower than 0.2 eV. Notably, B incorporation induces a shift in the d-band center of adjacent metal atoms, which indicates its pronounced impact on the catalytic activity of transition metals.