A theoretical study of CH4 dissociation on pure and gold-alloyed Ni(111) surfaces

Abstract

We present a density functional theory study of the first step of CH 4 adsorption on the Ni͑111͒ surface, dissociation into adsorbed CH 3 and H. The rupture of the C-H bond occurs preferentially on top of a Ni atom, with a dissociation barrier of about 100 kJ/mol ͑including zero point corrections͒. The transition state involves considerable internal excitation of the molecule. The active C-H bond is both stretched to 1.6 Å and tilted relative to the methyl group. A normal mode analysis shows that the reaction coordinate is mainly a C-H stretch, while the orientation of the C-H bond relative to the surface is responsible for the highest real mode. Alloying the surface with gold also affects the reactivity of the Ni atoms on adjacent surface sites. The dissociation barrier is increased by 16 and 38 kJ/mol for a Ni atom with one or two gold neighbors, respectively. We attribute these changes to a shift in the local density of d states at the nickel atoms in the neighborhood of gold.

Effect of Au and/or Mo Doping on the Development of Carbon and Sulfur Tolerant Anodes for SOFCs—A Short Review

“…The decrease in the catalytic activity of the 3Au-3Mo-Ni/GDC sample with respect to the non-modified Ni/GDC is in accord with the d-band center theory proposed by Norskov et al (Kratzer et al, 1996;Nørskov et al, 2011) and specifically dealing with the dissociation and dehydrogenation of CH 4 on the Au doped Ni surface. They proposed that the rate of CH 4 dehydrogenation will be retarded on the Au modified surface, due to the fact that the center of the d-band density of states shifts to lower energy below the Fermi level with respect to Ni.…”

Surface chemistry of catalysis by gold

“…The initial sticking probability of methane on a Ni surface with just 0.25 ML of gold fell to ~1 0% of the sticking value of the clean Ni(111) surface (166). DFT calculations revealed that the CH4 dissociation barrier on a Ni atom increased by 16 kJ/mol when a single Au neighbor was present (167). Two neighboring gold atoms, resulted in a 38 kJ/mol increase (the barrier to dissociation on a Ni(111) atom was calculated to be ~1 00 kJ/mol).…”

First-principles analysis of the C–N bond scission of methylamine on Mo-based model catalysts

“…To correlate the electronic structure of the surface and its catalytic properties, the d-band center partly describing the electronic effect of the surface, is calculated by the formula 25,26…”