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Probing the Structure and Dynamics of Interfacial Water with Scanning Tunneling Microscopy and Spectroscopy
Published on: May 27, 2018
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Water orientation on platinum surfaces controlled by step sites.
Naoki Nagatsuka1, Takumi Otsuki1, Shota Kamibashira1
1Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan.
The Journal of Chemical Physics
|September 3, 2024
Summary
Deuterated water on platinum surfaces shows D-down orientation at step sites. Oxygen pre-adsorption disrupts this, causing water dissociation and flat-lying configurations, impacting interfacial water orientation.
Area of Science:
- Surface Science
- Physical Chemistry
- Spectroscopy
Background:
- Understanding water adsorption on metal surfaces is crucial for catalysis and electrochemistry.
- The role of surface steps in molecular orientation is not fully understood.
- Deuterated water (D2O) offers a way to probe hydrogen bonding dynamics.
Purpose of the Study:
- To investigate the adsorption structure of deuterated water on stepped platinum surfaces.
- To determine the influence of step sites and oxygen pre-adsorption on water molecule orientation.
- To elucidate the role of hydrogen bonding in interfacial water configuration.
Main Methods:
- Heterodyne-detected sum-frequency generation (HD-SFG) spectroscopy under ultra-high vacuum.
- Utilizing a stepped platinum surface (Pt(553)).
- Density-functional theoretical (DFT) calculations for theoretical support.
Main Results:
- On pristine Pt(553), D2O at step sites acts as H-bond donors, leading to D-down orientation at terrace sites.
- Oxygen pre-adsorption at step sites causes spontaneous dissociation of D2O into hydroxyl (OD) species.
- Hydroxyl formation alters hydrogen bonding, causing D2O at terraces to adopt flat-lying configurations, reducing D-down orientation.
Conclusions:
- Surface steps critically control the net orientation of interfacial water molecules.
- Oxygen pre-adsorption significantly modifies water adsorption and orientation at step sites.
- Findings provide a reference for reactions at electrochemical interfaces involving water.
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