What question did this study set out to answer?

To investigate the mechanisms, coverage, and onset conditions of hydroxylation and molecular water adsorption on the α-Fe2O3(0001) surface across varied humidity and temperature ranges.

January 13, 2010The Journal of Physical Chemistry C291 citationsOpen Access

Water Adsorption on α-Fe2O3(0001) at near Ambient Conditions

SYSusumu Yamamoto TKTom Kendelewicz JNJohn T. Newberg

Key Points

To investigate the mechanisms, coverage, and onset conditions of hydroxylation and molecular water adsorption on the α-Fe2O3(0001) surface across varied humidity and temperature ranges.
Utilized ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) to analyze α-Fe2O3(0001) surfaces.
Conducted measurements at water vapor pressures up to 2 Torr and temperatures from 277 to 647 K (relative humidity ≤ 34%).
Performed depth profiling measurements to identify the vertical distribution of hydroxyl groups.
Hydroxylation begins at an extremely low relative humidity of 1 × 10−7% strictly at the topmost surface layer, reaching up to 1 monolayer coverage without a distinct threshold pressure.
Molecular water adsorption initiates at onsets ranging from ~2 × 10−5% to ~4 × 10−2% relative humidity depending on temperature and water vapor pressure.
Adsorbed water coverage reaches 1 monolayer at ~15% relative humidity and increases to 1.5 monolayers at 34% relative humidity.

Abstract

We have investigated hydroxylation and water adsorption on α-Fe2O3(0001) at water vapor pressures up to 2 Torr and temperatures ranging from 277 to 647 K (relative humidity (RH) ≤ 34%) using ambient-pressure X-ray photoelectron spectroscopy (XPS). Hydroxylation occurs at the very low RH of 1 × 10−7 % and precedes the adsorption of molecular water. With increasing RH, the OH coverage increases up to one monolayer (ML) without any distinct threshold pressure. Depth profiling measurements showed that hydroxylation occurs only at the topmost surface under our experimental conditions. The onset of molecular water adsorption varies from ∼2 × 10−5 to ∼4 × 10−2 % RH depending on sample temperature and water vapor pressure. The coverage of water reaches 1 ML at ∼15% RH and increases to 1.5 ML at 34% RH.

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Cite This Study

Yamamoto et al. (2010) studied this question.

synapsesocial.com/papers/6a01716ce8ec6bd19dcae241 https://doi.org/10.1021/jp909876t

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January 13, 2010The Journal of Physical Chemistry C291 citationsOpen Access

Water Adsorption on α-Fe2O3(0001) at near Ambient Conditions

SYSusumu Yamamoto TKTom Kendelewicz JNJohn T. Newberg

Key Points

To investigate the mechanisms, coverage, and onset conditions of hydroxylation and molecular water adsorption on the α-Fe2O3(0001) surface across varied humidity and temperature ranges.
Utilized ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) to analyze α-Fe2O3(0001) surfaces.
Conducted measurements at water vapor pressures up to 2 Torr and temperatures from 277 to 647 K (relative humidity ≤ 34%).
Performed depth profiling measurements to identify the vertical distribution of hydroxyl groups.
Hydroxylation begins at an extremely low relative humidity of 1 × 10−7% strictly at the topmost surface layer, reaching up to 1 monolayer coverage without a distinct threshold pressure.
Molecular water adsorption initiates at onsets ranging from ~2 × 10−5% to ~4 × 10−2% relative humidity depending on temperature and water vapor pressure.
Adsorbed water coverage reaches 1 monolayer at ~15% relative humidity and increases to 1.5 monolayers at 34% relative humidity.

Abstract

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Cite This Study

Yamamoto et al. (2010) studied this question.

synapsesocial.com/papers/6a01716ce8ec6bd19dcae241 https://doi.org/10.1021/jp909876t

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