Understanding the equilibrium conditions at the metal oxide/aqueous interface is a key component toward visualizing the structure of water in confined environments and differentiating the catalytic activity of transition-metal oxides. While ambient pressure X-ray photoelectron spectroscopy (AP-XPS) has been the primary technique to investigate the formation of a hydration layer on many surfaces, results over the extended relative humidity (RH) range accessible experimentally have not been compared quantitatively to theoretical predictions. With the use of first-principles theoretical methods and accumulated knowledge of AP-XPS spectral analysis, we do so here for a model surface, TiO2-terminated undoped SrTiO3(100) (STO). The measured distribution of OH and H2O coverages from vacuum up to the first hydration layer is in good agreement with a static density functional theory (DFT) configuration involving partial dissociation of H2O per Ti-atom mediated by H-bonding. Furthermore, ab initio molecular dynamics (AIMD) simulations at 300 K for select coverages (1/4, 1/2, and 1 ML) test the role of fluctuations and entropy in the competition between adsorption and dissociation with coverage. This comparison between theory and experiment for OH and H2O coverages on STO provides a foundation for a more quantitative assessment of the first hydration layer and associated competition between adsorption, dissociation, and H-bonding on transition-metal oxide surfaces.
Aschaffenburg, Daniel J., et al. "Accuracy in Resolving the First Hydration Layer on a Transition-Metal Oxide Surface: Experiment (AP-XPS) and Theory." Journal of Physical Chemistry. C, vol. 124, no. 39, Aug. 2020. https://doi.org/10.1021/acs.jpcc.0c05195
Aschaffenburg, Daniel J., Kawasaki, Seiji, Pemmaraju, Chaitanya Das, & Cuk, Tanja (2020). Accuracy in Resolving the First Hydration Layer on a Transition-Metal Oxide Surface: Experiment (AP-XPS) and Theory. Journal of Physical Chemistry. C, 124(39). https://doi.org/10.1021/acs.jpcc.0c05195
Aschaffenburg, Daniel J., Kawasaki, Seiji, Pemmaraju, Chaitanya Das, et al., "Accuracy in Resolving the First Hydration Layer on a Transition-Metal Oxide Surface: Experiment (AP-XPS) and Theory," Journal of Physical Chemistry. C 124, no. 39 (2020), https://doi.org/10.1021/acs.jpcc.0c05195
@article{osti_1769956,
author = {Aschaffenburg, Daniel J. and Kawasaki, Seiji and Pemmaraju, Chaitanya Das and Cuk, Tanja},
title = {Accuracy in Resolving the First Hydration Layer on a Transition-Metal Oxide Surface: Experiment (AP-XPS) and Theory},
annote = {Understanding the equilibrium conditions at the metal oxide/aqueous interface is a key component toward visualizing the structure of water in confined environments and differentiating the catalytic activity of transition-metal oxides. While ambient pressure X-ray photoelectron spectroscopy (AP-XPS) has been the primary technique to investigate the formation of a hydration layer on many surfaces, results over the extended relative humidity (RH) range accessible experimentally have not been compared quantitatively to theoretical predictions. With the use of first-principles theoretical methods and accumulated knowledge of AP-XPS spectral analysis, we do so here for a model surface, TiO2-terminated undoped SrTiO3(100) (STO). The measured distribution of OH and H2O coverages from vacuum up to the first hydration layer is in good agreement with a static density functional theory (DFT) configuration involving partial dissociation of H2O per Ti-atom mediated by H-bonding. Furthermore, ab initio molecular dynamics (AIMD) simulations at 300 K for select coverages (1/4, 1/2, and 1 ML) test the role of fluctuations and entropy in the competition between adsorption and dissociation with coverage. This comparison between theory and experiment for OH and H2O coverages on STO provides a foundation for a more quantitative assessment of the first hydration layer and associated competition between adsorption, dissociation, and H-bonding on transition-metal oxide surfaces.},
doi = {10.1021/acs.jpcc.0c05195},
url = {https://www.osti.gov/biblio/1769956},
journal = {Journal of Physical Chemistry. C},
issn = {ISSN 1932-7447},
number = {39},
volume = {124},
place = {United States},
publisher = {American Chemical Society},
year = {2020},
month = {08}}
Frank Ogletree, D.; Bluhm, Hendrik; Hebenstreit, Eleonore D.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 601, Issue 1-2https://doi.org/10.1016/j.nima.2008.12.155