Oxidation induced restructuring of Rh–Ga SCALMS model catalyst systems

Abstract

Supported catalytically active liquid metal solutions (SCALMS) have been receiving increasing attention recently. We investigated the oxidation behavior of macroscopic Rh-Ga alloy droplets and Rh-Ga model catalyst nanoparticles supported on SiO 2 /Si(100) with low Rh content (<2.5 at %) by x-ray photoelectron spectroscopy in ultra-high vacuum and under near-ambient pressure conditions using different photon energies and also using transmission electron microscopy. The experiments are accompanied by computational studies on the Ga oxide/Rh-Ga interface and Rh-Ga intermetallic compounds. For both Rh-Ga alloy droplets and Rh-Ga model catalyst nanoparticles, exposure to molecular oxygen leads to the formation of an oxide shell in which Rh is enriched. High-resolution transmission electron microscopy on the Rh-Ga nanoparticles confirms the formation of an approximately 4 nm thick gallium oxide film containing Rh. Based on ab-initio molecular dynamics and computational studies on the Ga 2 O 3 /Ga interface, it is concluded that Rh incorporation into the Ga 2 O 3 film occurs by substituting octahedrally coordinated Ga.

Isolated Rh atoms in dehydrogenation catalysis

“…Besides site isolation, several GaPd and GaRh systems show a change in the electronic structure of the active transition metal in the form of a charge transfer from Ga to the 4d band of Pd/Rh. This causes a shift of the d-band center further towards larger binding energies below the Fermi level 15,22,23 . For transition metal surfaces, it is generally accepted that the d-band center position and the availability of d-band hole states directly influence adsorption behavior and catalytic properties 24 .…”

Preparation of geometrically highly controlled Ga particle arrays on quasi-planar nanostructured surfaces as a SCALMS model system

“…+1.25 e for Rh in Ga 2 O 3 (ref. 28) (PtGa oxide 4f doublet at 75.7 eV and 72.4 eV with Δ = 3.32 eV). 26,27…”

Molecular Dynamics and Machine Learning in Catalysts

“…Ab initio molecular dynamics, which combines molecular dynamics with force directly calculated from the electronic structure, is a helpful method in the theoretical calculations of chemical reactions [43]. The electronic structure is solved directly at each step, and therefore it allows for bond breaking and formation [44,45].…”

“…Furthermore, a more intuitive dynamic process can be seen with the AIMD methods. Wittkamper et al [43] studied the restructuring of the Rh-Ga model because of the oxidation behavior. In this research, the simulation results were consistent with the experiments.…”