Atomic and molecular adsorption on RhMn alloy surface: A first principles study

Competition between stability of icosahedral and cuboctahedral morphologies in bimetallic nanoalloys

In this study, we investigated the heating process for pure (Rh₅₅ and Cu₅₅), single dopant (Rh₁Cu₅₄ and Rh₅₄Cu), core@shell (Rh₁₃@Cu₄₂ and Cu₁₃@Rh₄₂), and alloy (Rh₁₃Cu₄₂, Rh₄₂Cu₁₃) nanoclusters in two structures (cuboctahedral and icosahedral) from 0 to 2000 K using molecular dynamics (MD) simulations. Our aim was to investigate the effects of composition and chemical arrangement on the kinetic and thermodynamic stability of Rh-Cu bimetallic nanoalloys. Our results indicated that Cu₅₅, Ir₅₅, Rh₁Cu₅₄, Rh₅₄Cu, and Cu₁₃@Rh₄₂ in the cuboctahedral and icosahedral structures and Rh₄₂Cu₁₃ in the icosahedral structure did not experience any transformation with the exception of melting. It was also observed that the cuboctahedral Rh₄₂Cu₁₃ shows a solid-solid transformation to the icosahedral structure before the melting point. It is also observed that Rh₁₃@Cu₄₂ and Rh₁₃Cu₄₂ nanoclusters in both structures exhibit a transition to a pseudo-spherical structure before the melting point. Our results also illustrated that the Rh and Cu atoms tend to lie in the inner and outer shells of the nanoclusters, respectively. We have also discussed the changes in the melting points of the doped nanoclusters in the different arrangements.

Mn monolayer modified Rh for syngas-to-ethanol conversion: a first-principles study

Rh is unique in its ability to convert syngas to ethanol with the help of promoters. We performed systematic first-principles computations to examine the catalytic performance of pure and Mn modified Rh(100) surfaces for ethanol formation from syngas. CO dissociation on the surface as well as CO insertion between the chemisorbed CH(3) and the surface are the two key steps. The CO dissociation barrier on the Mn monolayer modified Rh(100) surface is remarkably lowered by ~1.5 eV compared to that on Rh(100). Moreover, the reaction barrier of CO insertion into the chemisorbed CH(3) group on the Mn monolayer modified Rh(100) surface is 0.34 eV lower than that of methane formation. Thus the present work provides new mechanistic insight into the role of Mn promoters in improving Rh's selectivity to convert syngas to ethanol.