Low-temperature partial dissociation of water on Cu(1 1 0)
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Self-ionization of water
Low-energy electron diffraction
Hydroxyl radical
Steps at high-index metallic surfaces display higher chemical reactivity than close-packed surfaces and may give rise to selective adsorption and partial dissociation of water. Inspired by differential desorption experiments, we have studied the adsorption and dissociation of water clusters and one-dimensional wires on Pt(211) by density functional theory and molecular dynamics simulations. These calculations reveal that water at the step edges of Pt(211) adsorbs more weakly than at Pt(221), but partial dissociation of adsorbed water clusters is energetically competitive. We observe that the one-dimensional structure proposed experimentally can be realized only by partially dissociated water wires. In addition, weaker adsorption allows the formation of structures in which a number of water molecules detach from the step and form weak hydrogen bonds with the terrace. This study is further extended to the energetics of small water clusters on (211) surfaces of Ir, Rh, and Pd.
Self-ionization of water
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Self-ionization of water
Charge density
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Self-ionization of water
Water-gas shift reaction
Bond-dissociation energy
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Self-ionization of water
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The coadsorption of water and preadsorbed oxygen on Ru{0001) was studied by synchrotron-based high-resolution x-ray photoelectron spectroscopy. A dramatic change was observed in the interaction of water with oxygen between low and high oxygen precoverages. Low oxygen coverages below 0.18 ML induce partial dissociation, which leads to an adsorbed layer of ${\text{H}}_{2}\text{O}$ and OH. Around half the oxygen atoms take part in this reaction. All OH recombines upon heating to 200 K and desorbs together with ${\text{H}}_{2}\text{O}$. Oxygen coverages between 0.20 and 0.50 ML inhibit dissociation, instead a highly stable intact water species is observed, which desorbs at 220 K. This species is significantly more stable than intact water on the clean surface. The stabilization is most likely due to the formation of hydrogen bonds with neighboring oxygen atoms. For intermediate oxygen coverages around 0.18 ML, the dissociation behavior depends on the preparation conditions, which points toward possible mechanisms and pathways for partial dissociation of water on Ru{0001}.
Self-ionization of water
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Self-ionization of water
Passivation
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Based on electron and vibration approximate means and the density function theory B3LYP,the ΔG° and equilibrium pressures of adsorption and dissociation reactions of H2 and water vapor on Pt surface have been calculated.The adsorption,dissociation and coadsorption actions of H2 and water were analyzed.According to the ΔG°,hydrogen molecule combines with metal atoms in single atom,and water vapor molecule has no tendency to dissociate on Pt surface.The dissociation of hydrogen molecule would hold back the direct adsorption of water vapor molecules on Pt surface.The structures of Pt-H(OH2)+n(n=1,2,3)hydroniums were optimized.According to the mulliken overlap populations,Pt-H(OH2)+ is not stable or produced.Hydrogen isotope exchange occurs between hydration layer and D atoms which adsorb on Pt surface via intermediates(H2O)nD+(ads)(n≥2)
Self-ionization of water
Kinetic isotope effect
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A new reactive and polarizable molecular model was developed to describe HCl dissociation in liquid water and used to investigate HCl behavior at the air-water interface. It was found that the mechanism of HCl accommodation at the air-water interface began with its hydrogen pointing toward the water as it approached from the air. This was followed by dissociation into a contact ion pair once solvated at the air-water interface with the hydronium oriented more toward the air than the chloride on average. In comparison with NaCl, HCl showed some similar behavior in that its contact ion pair was stabilized at the air-water interface in comparison with the bulk. However, dissociated HCl had a greater propensity for the air-water interface than NaCl due to the fact that the hydronium ion was more surface active than sodium.
Hydronium
Self-ionization of water
Hydrogen chloride
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Self-ionization of water
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Using first-principles calculations we have studied the reactions of water over Ti-decorated C60 in order to assess the possibility of using this system as a catalyst for water dissociation. Our results show that a single water molecule dissociates exothermically with a small energy barrier on a single Ti atom adsorbed on C60. After dissociation, both H+ and OH− ions bind strongly to the Ti atom, which serves as an effective reactive center that facilitates further water splitting. When a second water molecule is introduced, we observe the formation of a hydrogen molecule with a comparably small activation barrier. When the coverage of Ti on C60 is increased, the formation of Ti dimer does not change the catalytic effect of Ti∕C60 complex very much. Our results provide fundamental insights into the mechanisms of water dissociation on such a prototypical nanostructure and suggest that Ti-decorated C60 could be exploited as a catalyst for water splitting to generate hydrogen.
Self-ionization of water
Water dimer
Hydrogen atom
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