The reactivity of oxides with water vapor

An ångström-sized window on the origin of water in the inner solar system: Atomistic simulation of adsorption of water on olivine

“…Note that for S2 a very specialized adsorption geometry gives rise to a higher adsorption energy and that S1, in spite of being underbonded does not adsorb any water because of its location deeper in the surface. The effect of underbonding on the strength of the adsorption sites was also observed by Leed and Pantano [66] on glass fracture surfaces. The adsorption energies observed in the present work are in excellent agreement with those observed in previous studies [39,67].…”

“…For all the runs, the H coordinates to O OX and the O H 2 O bonds to the Mg ions on the surface, as typical for coordinative adsorption [66]. Angles between the water molecule and the surface ions sometimes resemble those observed between water molecules.…”

Coordination chemistry of Ca sites at the surface of nanosized hydroxyapatite: interaction with H2O and CO

“…The shape of the curves, in all investigated samples, is typical of highly heterogeneous surfaces in that the adsorption enthalpy decreases from a quite high zero-coverage value [q 0 = (−D ads H) 0 ≥ 100 kJ mol −1 ] down to a value approaching the latent enthalpy of liquefaction of water [(−D LIQ H) = 44 kJ mol −1 ] only at high coverage. The enthalpy value was larger than 44 kJ mol −1 in all cases (including the silicabased model systems), and in the whole range of H 2 O pressure examined, it was confirmed that all investigated samples are typical hydrophilic surfaces [37,38].…”

“…A well-established stepwise procedure was followed [37,38], which allowed us to determine, during the same experiment and for subsequent small increments of the adsorptive, both adsorbed amounts and integral heats evolved, as a function of the increasing equilibrium pressure. This latter was monitored by a transducer gauge (Ceramicell 0-100 Torr, Varian).…”

X-ray diffraction study of the hydrogen reduction of NiO/α-Al2O3 steam reforming catalysts

“…Fubini et al discussed the reactivity of oxides with water vapor [55] and found that H 2 O chemisorption occurs in three principal modes: hydrogen-bonded, co-ordinative, and dissociative, with enthalpies of adsorption in the ranges 50-70 kJ mol −1 , 70-120 kJ mol −1 , and >120 kJ mol −1 , respectively. Furthermore, the enthalpy of the dissociative mode and the amount adsorbed increased with the hydrophilic nature of the oxide.…”