jp074472c_si_001.pdf (75.3 kB)
Adsorption and Dissociation of H2O on a W(111) Surface: A Computational Study
journal contribution
posted on 2007-11-22, 00:00 authored by Hsin-Tsung Chen, Djamaladdin G. Musaev, M. C. LinThe adsorption and dissociation of water on a W(111) surface have been studied at the density functional
theory (DFT) level in conjunction with the projected augmented wave approach. The potential energy surface
of the water decomposition on the W(111) surface was constructed. It was shown that the barriers for the
stepwise H2O dehydrogenation reaction, H2O → 2H(ads) + O(ads), are 1.8 (for HO−H bond activation) and
15.9 (for the O−H bond activation) kcal/mol. The entire process, W(111) + H2O → 2H(ads) + O(ads), is 54.4
kcal/mol exothermic. Calculations show that the formation of W(111)−O + H2(gas) from W(111) + H2O is
also exothermic by 23.7 kcal/mol. These results are in good agreement with the temperature-programmed
desorption and high-resolution electron energy loss spectroscopy data. On the basis of the calculated PES,
we predicted kinetic rate constants for the dissociative adsorption of H2O on the W(111) surface. The structure,
vibrational frequency, and binding energy of the W(111)−H2O, W(111)−OH, W(111)−O, and W(111)−H
systems were also predicted. It was shown that the most favorable structure of W(111)−H2O corresponds to
the coordination of water through its oxygen lone pairs with the W(111) surface (at its top position). The
preferable binding sites for the OH, O, and H fragments are top, top, and bridge sites, respectively. The
stepwise dissociative adsorption mechanism of H2O on the W(111) surface has also been confirmed by DFT
molecular dynamics simulations.