The rate limiting step in the steam reforming of methane is the dissociative chemisorption of methane on a Ni catalyst.  DFT-based electronic structure methods are used to map out reaction pathways for this process on several Ni and Pt surfaces, and a full-dimensional fully quantum reaction path model is used to compute state-resolved dissociative sticking probabilities.  This model is based on an expansion in the adiabatic vibrational states of the methane, and a sudden approximation is used to incorporate the effects of lattice motion. The barriers to reaction vary with lattice motion for all surfaces, leading to a strong increase in reactivity with temperature. Comparisons are made with recent experiments on Ni(100), Ni(111), Pt(111) and Pt(110)-(1x2).  Our model successfully explains the magnitude of the reactivity, its variation with energy and temperature, and the observed increase in reactivity with vibrational excitation of the methane.

Dynamics of methane dissociation on Ni and Pt surfaces

245th National Meeting (2013)

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