Adsorption Kinetics Of H2O Research Articles

Adsorption kinetics of H2O on graphene surface based on a new potential energy surface

The interaction between water and graphene is important for understanding the thermodynamic and kinetic properties of water on hydrophobic surfaces. In this study, we constructed a high-dimensional potential energy surface (PES) for the water-graphene system using the many-body expansion scheme and neural network fitting. By analyzing the landscape of the PES, we found that the water molecule exhibits a weak physisorption behavior with a binding energy of about − 1000 cm−1 and a very low diffusion barrier. Furthermore, extensive molecular dynamics were performed to investigate the adsorption and diffusion dynamics of a single water on a graphene surface at temperatures ranging from 50 to 300 K. Potential-of-mean-forces were computed from the trajectories, providing a comprehensive and accurate description of the water-graphene interaction kinetics.

Diffusion mechanism of water vapour in a zeolitic tuff rich in clinoptilolite

The adsorption kinetics of H2O in a clinoptilolite rich zeolitic tuff was experimentally investigated at 18°C. In the identification of the diffusion mechanism the isothermal adsorption model equation was used. It was found out that the intraparticle mass transfer becomes more dominant over the heat transfer with increase in particle size and the adsorptive dose pressure. Although initially intraparticle mass transfer was the controlling resistance later external heat transfer also contributes to the transfer mechanism.

Kinetic Isotope Quantum Effects in the Adsorption of H2O and D2O on Porous Carbons

This paper describes an investigation of the adsorption characteristics of H2O and D2O on two activated carbons, BAX950, containing a range of micro- and mesoporosity, and G209, a predominantly microporous material. Adsorption kinetics of H2O and D2O on activated carbon BAX950 were studied over temperature ranges of 293−313 K and 278−303 K, respectively. The adsorption/desorption of H2O and D2O were also studied on activated carbon G209 at 298 K. The adsorption isotherms for H2O and D2O agree well while greater adsorption hysteresis was observed for H2O compared with D2O. Comparison of the adsorption kinetic behavior of H2O and D2O indicated a kinetic isotope effect. The trends in isotherm hysteresis, kinetic parameters, and activation energies are attributed to quantum effects, which are the source of differences in intermolecular hydrogen bonding in H2O and D2O adsorbates and bonding between these adsorbates and surface oxygen functional groups. The effects of confinement in pores on adsorbate structure are discussed.

H2O adsorption kinetics on Si(111)7×7 and Si(111)7×7 modified by laser annealing

The adsorption kinetics of H2O on Si(111)7×7 and Si(111)7×7 modified by laser annealing were studied using laser-induced thermal desorption and temperature-programmed desorption techniques at temperatures between 180 and 800 K. The laser-annealed Si(111)7×7 surface displayed an enhanced initial reactive sticking coefficient for H2O compared with the unmodified Si(111)7×7 surface. At 180 K, the initial reactive sticking coefficient was S0=6.9×10−1 on laser-annealed Si(111)7×7 compared with S0=1.9×10−2 on unmodified Si(111)7×7. This larger initial sticking coefficient is attributed to the creation of a more reactive surface structure formed by the laser annealing process. At higher oxygen coverages, the reactivity of the laser-annealed surface changed and displayed much slower H2O adsorption rates that were similar to the kinetics on Si(111)7×7. The decreasing initial reactive sticking coefficient versus increasing surface temperature suggested a precursor-mediated adsorption mechanism on both the Si(111)7×7 and laser-annealed Si(111)7×7 surfaces. After long H2O exposures, the oxygen coverage saturated at θO≊0.35 monolayers on Si(111)7×7 for temperatures between 300 and 700 K. At higher surface temperatures, the saturation coverage increased prior to SiO desorption at temperatures above 900 K. This increase was attributed to the creation of additional dangling bond adsorption sites following H2 desorption at temperatures above 700 K.

Slow adsorption kinetics of H2O on Si(111)

Slow adsorption kinetics of H2O on Si(111)