Reaction Mechanism for Hydrogen Production via Methane Pyrolysis on a Dynamic Liquid Ga-Fe-Ni Catalyst

Abstract

Dynamic liquid metal alloys have been promising for catalytic green hydrogen (H2) production through methane pyrolysis. Owing to their atomic mobility, liquid metal catalysts have a fluidic atomic structure in which obtaining reaction energies and kinetic barriers hinges on reliable geometrical descriptions of atomic arrangements. Here, the catalytic reaction mechanism for methane pyrolysis on the surface of molten Ga-Fe-Ni as the catalyst is investigated, using an approach based on fully dynamic sampling of ab initio molecular dynamic trajectories. The results reveal that the adsorption energy for the first C & horbar;H bond breaking in methane is notably enhanced from 2.2 eV on liquid Ga to 1.2 eV on molten Ga-Fe-Ni. The mobility of dissolved Fe and Ni atoms plays a critical role for activation of Ga atoms on the alloy surface, facilitating charge transferring from solvent atoms (electron donor) to solute atoms (electron acceptor), thereby modulating electronic structure. The dissociated hydrogen atoms, with a low kinetic barrier of approximately 0.6 eV computed via the blue moon ensemble method, can easily bond together, desorbing as H2 molecules from the surface. Our findings highlight that mobile dissolved species in liquid metal matrix can bestow unique catalytic activity to solvent atoms by modifying electronic structure.