Water dissociation on Ni(100) and Ni(111): Effect of surface temperature on reactivity

Abstract

Water adsorption and dissociation on Ni(100) and Ni(111) surfaces are studied using density functional theory calculations. Water adsorbs on top site on both the surfaces, while H and OH adsorb on four fold hollow and three fold hollow (fcc) sites on Ni(100) and Ni(111), respectively. Transition states (TS) on both surfaces are identified using climbing image-nudged elastic band method. It is found that the barrier to dissociation on Ni(100) surface is slightly lower than that on Ni(111) surface. Dissociation on both the surfaces is exothermic, while the exothermicity on Ni(100) is large. To study the effect of lattice motion on the energy barrier, TS calculations are performed for various values of Q (lattice atom coordinate along the surface normal) and the change in the barrier height and position is determined. Calculations show that the energy barrier to reaction decreases with increasing Q and increases with decreasing Q on both the surfaces. Dissociation probability values at different surface temperatures are computed using semi-classical approximation. Results show that the influence of surface temperature on dissociation probability on the Ni(100) is significantly larger compared to that of Ni(111). Moreover, on Ni(100), a dramatic shift in energy barrier to lower incident energy values is observed with increasing surface temperature, while the shift is smaller in the case of Ni(111).

HOD on Ni(111): Ab Initio molecular dynamics prediction of molecular beam experiments

“…c) Email: g.j.kroes@chem.leidenuniv.nl more and more degrees of freedom (DOFs) and details in the potential energy surface (PES). 3,4,[7][8][9][10][11]15,[17][18][19][20][21][22][23][24]26,30 The dissociation of water on metal surfaces is a late barrier process 3,4,15 which is greatly promoted by vibrational energy in the molecule, 3,4,20,21 and it exhibits large mode 9,10 and bond 19 specificity in agreement with Polanyi's rule. 31 This is also in agreement with results of the sudden vector projection (SVP) model 5,6 which predicts large couplings between the vibrational modes of the reactant and the reaction coordinate at the transition state.…”

“…For both molecules, at high incidence energies, we observe direct dissociation with a late barrier, the height of which also depends on the displacement(s) of the surface atom(s) above which the reaction happens. 3,5,26,32,33 State-selected molecular beam experiments have been performed on both methane 34,35 and water. 3 Using Ab Initio Molecular Dynamics (AIMD) paired with a semiempirical density functional, it has been possible to reproduce the experiments with chemical accuracy (i.e., ≈4.2 kJ/mol) for methane (specifically the CHD 3 isotopologue) on Ni(111), 35 Pt(111), 34 and Pt(211).…”

First-principles study of oxygen coverage effect on hydrogen oxidation on Ni(111) surface

“…A lot of DFT studies have been carried out for different surface orientations of Ni, such as (1 1 1) [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28], (1 0 0) [15,[25][26][27][28][29][30], and (2 1 1) [21,22,31]. Most of the papers are discussed on the dissociation of H 2 O to OH and H [10][11][12][13]16,22], as a one of the steps of steam reforming reaction on Ni surface.…”

Enhancing methane dissociation with nickel nanoclusters

“…It was previously reported for CH 4 [24,27] and H 2 O [63,64] dissociation on nickel surfaces reactivity depends significantly on surface temperature. Surface temperature effect was well explained with an electronic coupling parameter b, which is the first derivative of energy i.e., force.…”