(641c) Combined DFT and Kinetic Monte Carlo Studies of Formic Acid Decomposition on Au18 Nanoclusters
In this work, we further probe the activity of Au18 clusters by performing comprehensive Kinetic Monte Carlo (KMC) simulations with our DFT results. KMC simulations outrank mean-field models in terms of fidelity, by being able to capture spatial inhomogeneities in the site distribution of Au18, as well as correlations due to adsorbate ordering. We indeed noticed strong adsorbate-adsorbate interactions for this system. To factor in their effects on the reaction energetics, we employ a cluster expansion, parameterizing the interaction energies of adsorbates in terms of point and multi-body interactions.5
Our simulations reveal that the TOF of H2 on Au18 is much closer to the experimental TOF compared to extended Au(211)/(100) surfaces,4 and is thus a likely model of the active site for FA decomposition. A triangular ensemble of three Au atoms, each with a coordination number of five (CN=5 sites), is found to be the active site. Our work will offer valuable insights into the molecular pathways of FA decomposition, and serve to guide future efforts to optimize the shape and size of Au catalysts for the FA decomposition reaction.
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