Adsorption, Desorption, and Displacement Kinetics of H2O and CO2 on Forsterite, Mg2SiO4(011)

Journal Article · Thu Dec 18 04:00:00 EST 2014 · Journal of Physical Chemistry C, 118(50):29091-29100

DOI:https://doi.org/10.1021/jp504187y· OSTI ID:1188934

Smith, R. Scott; Li, Zhenjun; Dohnalek, Zdenek; Kay, Bruce D.

We have examined the adsorbate-substrate interaction kinetics of CO2 and H2O on a natural forsterite crystal surface, Mg2SiO4(011), with 10-15% of substitutional Fe2+. We use temperature programmed desorption (TPD) and molecular beam techniques to determine the adsorption, desorption, and displacement kinetics for H2O and CO2. Neither CO2 nor H2O has distinct sub-monolayer desorption peaks but instead both have a broad continuous desorption feature that evolve smoothly into multilayer desorption. Inversion of the monolayer coverage spectra for both molecules reveals that the corresponding binding energies for H2O are greater than that for CO2 on all sites. The relative strength of these interactions is the dominant factor in the competitive adsorption/displacement kinetics. In experiments where the two adsorbates are co-dosed, H2O always binds to the highest energy binding sites available and displaces CO2. The onset of CO2 displacement by H2O occurs between 65 and 75 K.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1188934
• Report Number(s): PNNL-SA-102294; 48154; KC0301020
• Journal Information: Journal of Physical Chemistry C, 118(50):29091-29100, Journal Name: Journal of Physical Chemistry C, 118(50):29091-29100
• Country of Publication: United States
• Language: English

Related Subjects

Environmental Molecular Sciences Laboratory