Thermal Stability of Single Atom Metal Catalysts: ReaxFF Molecular Dynamics Study

The catalytic activity of metal catalysts is closely related to its coordination unsaturation: The higher coordination unsaturation is, the better catalytic effect is in general. The single-atom catalyst (SAC or ad-atom) model has the smallest coordination number on metal surface and thus exhibits high catalytic activity, but the stability of SAC still need to be studied in detail. In this work, we used LAMMPS (large-scale atomic/molecular massively parallel simulator) for large-scale molecular dynamics simulation based on Reactive Force Field (ReaxFF) to study the thermal stability of the single atom model. The simulation results show that only Fe-l/Fe (100) catalyst can be stable at high temperature (>500 K), while other SAC models will occur that single atom aggregates to form large nanoparticles or moves to subsurface as temperature increases. In the meanwhile, the dynamic behavior of Ni-l/Ni (111) catalyst under H-2 and O-2 atmosphere was also studied was found that compared with simulation results in vacuum, the H-2 and O-2 atmosphere improved the stability of the catalyst to some extent.