Quantum dynamics of dissociative chemisorption of CH4 on metal surfaces
The dissociation of CH4 into CH3 + H on a metal surface is the rate determining step in processes which produce hydrogen, such as steam reforming and catalytic partial oxidation. Ultimately, we want to study the dissociation of methane on Ni(111) and Pt(111) quantum mechanically while taking into account all degrees of freedom of the molecule. A major challenge we are working on is how to represent the 15-dimensional potential energy surface. An important goal of the research is to establish the reasons for vibrational selectivity of reaction (pre-excitation of specific vibrational modes enhances the reaction more than of other modes).
As performing full-dimensional quantum dynamical calculations on these system is quite challenging, we are also testing the Ab Initio Molecular Dynamics (AIMD) method for these systems. One of our goals is to derive specific reaction parameter density functionals capabale of describing these reactions with chemical accuracy. An extra challenge to be addressed is that for this approach to work it will also be necessary to treat the surface phonons accurately.
For an overview of the exciting questions that need to be addressed for these reactions, see the paper "Frontiers in Surface Scattering Simulations, G.J. Kroes, Science 321, 794-797 (2008)", and "Towards chemically accurate simulation of molecule-surface reactions, G.J. Kroes, Phys. Chem. Chem. Phys.14, 14966-14981 (2012)". For first results of the group, see our recent paper "Ab Initio Molecular Dynamics Calculations versus Quantum-State Resolved Experiments on CHD3 + Pt(111): New Insights into a Prototypical Gas-Surface Reaction, F. Nattino, H. Ueta, H. Chadwick, M. van Reijzen, R.D. Beck, B. Jackson, M.C. van Hemert, and G.J. Kroes, J.Phys.Chem.Lett.5, 1294-1299 (2014)".