Molecular Dynamics Study on Metal-Deposited Iron Oxide Nanostructures and Their Gas Adsorption Behavior

This study presents a comprehensive theoretical and experimental study on the deposition mechanism of precious metal nanoparticles (e.g., Au, Pt, Ag, and Pd) onto iron oxides (e.g., alpha-FeOOH, alpha-Fe2O3, and Fe3O4), which can be generated through a hydrothermal synthesis at ambient conditions. By using molecular dynamics (MD) method, the surface interaction energy between metal nanoparticle and iron oxide surface can be quantified. The analysis shows that the total potential energy of the metal nanoparticles decreases significantly when the metal particles are deposited onto porous or defected sites. The interaction is heavily dependent on nanoparticle size, elemental species, and surface structure of the iron oxide (porous or defects). The van der Waals force was found to play a dominant role in the deposition process. The MD simulation shows that the gases (e.g., CO, propene) on such nanocomposites have a lower diffusion coefficient at the Au/Fe2O3 surface and hence enhance catalytic activity, which may help understand the catalytic mechanism of metal oxide nanocomposites.