(169af) Modeling H-D Exchange in Supported Catalytically Active Liquid Metal Solutions Using Reactive Molecular Dynamics

Supported catalytically active liquid metal solutions (SCALMS) represent a unique class of materials owing to the dynamic nature of late transition metals introduced to a liquid metal matrix. SCALMS’ bi-functional nature can enable propane dehydrogenation reactions while achieving exceptional H₂ absorption capacity. These intrinsic properties allow for process intensification via simultaneous catalytic conversion and reactant separation. However, the atomic structure of SCALMS, specifically PdGa, and the interactions with gaseous H₂ and relevant C₃ species (propane/propylene) is challenging to probe experimentally. Density functional theory (DFT) allows for the quantum mechanical description of short-range materials but is incapable of accurately describing liquid metal systems due to the dynamically unstable configurations of the liquid solution. Reactive molecular dynamics, using the ReaxFF reactive force field, facilitates the study of these dynamic systems as well as transport and kinetic phenomena directly observed over time.

We present a ReaxFF-based investigation of the Pd-Ga-C-H system to understand the ensemble average Pd interactions with molecular or atomic hydrogen within the liquid matrix as well as induced surface responses under the presence of gaseous alkanes. To ensure our model describes both the representative structures and kinetics of experimentally synthesizable SCALMS, we evaluate H₂ permeability through the liquid and the equilibrium H₂ absorption as a function of Pd content. To achieve thermodynamically stable PdGaH phases, a Grand-Canonical Monte Carlo (GCMC) methodology is applied which permits probing H-loading at various temperatures, H₂ pressures, and Pd contents for experimental validation. Additionally, we introduce into our simulations a mixed propane/propylene gas phase to study adsorption-induced surface segregation of Pd to the surface of the liquid matrix which has important implications towards the H₂ dissociative mass-activity of the late-transition metals within SCALMS.