Methane dissociation on Pt(111), Ir(111) and Ptlr(111) surface: A density functional theory study

摘要

A periodic density functional theory (DFT) was utilized to calculate the dissociation process of methane (CH_4) on Pt(111), Ir(111) and Ptlr(111) surfaces. As compared to the adsorption energy, the most stable configurations of methane, methane dissociation species and co-adsorption of CH_X (x = 0-3) with H were obtained. The kinetic results of the CH_4 dissociation indicated that the dissociating of CH_4 into CH_3 and H is the rate-limiting step on the Ptlr(111) and Ir(111) surfaces. CH was the most abundant species that was difficult to dehydrogenate into C and H. Particularly, the activation barrier for CH3 → CH_2 + H and CH_2 → CH + H on the Pt( 111) surface is 3.5 and 1.4 times, respectively, higher than that on the Ptlr( 111) surface. According to the thermodynamics principles, the successive dehydrogenation of CH_4 preferred to take place on the Ptlr surface.