Dissociative chemisorption of CH 4 on transition-metal surfaces, representing the rate-limiting step in methane steam reforming, has been shown experimentally to be strongly mode selective. To understand the mode selectivity, a twelve-dimensional global potential energy surface is developed for CH 4 interacting with a rigid Ni(111) surface based on a large number of density functional theory points. The reaction dynamics is investigated using an eight-dimensional quantum model, which includes representatives of all four vibrational modes of methane. After correcting for surface effects, key experimental observations, including the mode selectivity, are well reproduced. These theoretical results, along with mechanistic analysis, provide insights into this industrially important heterogeneous reaction.

Dissociative chemisorption is the initial and often rate-limiting step in many heterogeneous processes. As a result, an in-depth understanding of the reaction dynamics of such processes is of great importance for the establishment of a predictive model of heterogeneous catalysis. Overwhelming experimental evidence has suggested that these processes have a non-statistical nature and excitations in various reactant modes have a significant impact on reactivity. A comprehensive characterization of the reaction dynamics requires a quantum mechanical treatment on a global potential energy surface. In this review, we summarize recent progress in constructing high-dimensional potential energy surfaces for polyatomic molecules interacting with transition metal surfaces based on the plane-wave density functional theory and in quantum dynamical studies of dissociative chemisorption on these potential energy surfaces. A special focus is placed on the mode specificity and bond selectivity in these gas-surface collisional processes, and their rationalization in terms of the recently proposed Sudden Vector Projection model.

By exciting the rotational modes of vibrationally excited CHD3(v1 = 1, JK), the reactivity for the Cl + CHD3 → HCl + CD3 reaction is observed enhanced by as much as a factor of two relative to the rotationless reactant. To understand the mode specificity, the reaction dynamics was studied using both a reduced-dimensional quantum dynamical model and the conventional quasi-classical trajectory method, both of which reproduced qualitatively the measured enhancements. The mechanism of enhancement was analyzed using a Franck-Condon model and by inspecting trajectories. It is shown that the higher reactivity for higher J states of CHD3 with K = 0 can be attributed to the enlargement of the cone of acceptance. On the other hand, the less pronounced enhancement for the higher J = K states is apparently due to the fact that the rotation along the C-H bond is less effective in opening up the cone of acceptance.