Energetics and dynamics of CH4 and H2O dissociation on metal surfaces

Abstract

Dissociative chemisorption is one of the most significant steps in heterogeneous catalysis. The rate-limiting step for industrially important processes such as water gas-shift reaction and steam reforming of methane involves the dissociative chemisorption of water and methane, respectively. These reactions exhibit interesting mode-specificity and show a strong dependence on the surface temperature of the catalyst. The metals commonly used in industry as catalysts for these two processes have their own limitations. Certain bimetallic surfaces and subsurface alloys are suggested, which could be regarded as potential catalysts for these two industrial processes. How transition states are modified by the motion of the lattice atom during the reactions are shown using electronic structure calculations. In the present review, we have focused on the lattice atom distortion in the transition state, semi-classical tunnelling probability, and the influence of surface temperature on reactivity. Quantum dynamics study for H O dissociation on metal surface is explored using three-dimensional London-Eyring-Polanyi-Sato potential energy surface. A full quantum mechanical approach following reaction path Hamiltonian is also studied by including the effects of lattice motion and site averaging. The effects of initial vibrational mode on reactivity are reported. Vibrational efficacy is examined in terms of vibrational non-adiabatic couplings.