Formation of the titanium oxyl at an electrochemical interface: limiting the role of solvent re-orientation in strong electric fields
Abstract
The oxidation of water at surfaces requires reactive and metastable intermediates such as surface adsorbed and often electron deficient oxygen. An outstanding question is whether forming these intermediates depends primarily on the energetics of adsorption associated with the reorganization of bonds at a vacuum interface, or whether it must include contributions from the re-orientation of water dipoles and ions within the aqueous electrolyte that could lower the free energy. Time-resolved mid-infrared experiments in an attenuated total reflection geometry have detected the terminal oxygen, the titanium oxyl, by a vibration that forms underneath it. The vibration was shown to couple to the librational modes of water by a Fano resonance. Here, we show that the picosecond formation of the titanium oxyl’s vibration is invariant across interfaces that change the density of librational modes (air, pH 7, pH 13, and pD 13), as detected by significant modifications of the coupled line-shape. Across the interfaces, we report a common rate constant (0.56 +/- 0.08 ps) and half rise (1.76 +/- 0.39 ps). This demonstrates that the reorganizational energy associated with solvent re-orientation is limited to affecting the ultrafast (400 fs) time resolution of the experiment characteristic of activation-less reactions and bond-reorganization. Furthermore, the formation kinetics are well-fit by a logistic function that describes an autocatalytic reaction and the surface population of titanium oxyl with excitation is well modelled by the Langevin equation. Both suggest that the invariant picosecond rise is due to a re-orientation of the titanium oxyl and its p-polarized vibrational dipole with respect to the strong Helmholtz electric field common to the probed interfaces.
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BibTeX
@misc{zayka2026formation,
title = {{Formation of the titanium oxyl at an electrochemical interface: limiting the role of solvent re-orientation in strong electric fields}},
author = {Paul Zayka and James Stewart and Tanja Cuk},
howpublished = {ChemRxiv},
year = {2026},
month = sep,
doi = {10.26434/chemrxiv.15008992/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008992/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Formation of the titanium oxyl at an electrochemical interface: limiting the role of solvent re-orientation in strong electric fields
AU - Paul Zayka
AU - James Stewart
AU - Tanja Cuk
PY - 2026
DA - 2026/09/17
PB - ChemRxiv
DO - 10.26434/chemrxiv.15008992/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008992/v1
AB - The oxidation of water at surfaces requires reactive and metastable intermediates such as surface adsorbed and often electron deficient oxygen. An outstanding question is whether forming these intermediates depends primarily on the energetics of adsorption associated with the reorganization of bonds at a vacuum interface, or whether it must include contributions from the re-orientation of water dipoles and ions within the aqueous electrolyte that could lower the free energy. Time-resolved mid-infrared experiments in an attenuated total reflection geometry have detected the terminal oxygen, the titanium oxyl, by a vibration that forms underneath it. The vibration was shown to couple to the librational modes of water by a Fano resonance. Here, we show that the picosecond formation of the titanium oxyl’s vibration is invariant across interfaces that change the density of librational modes (air, pH 7, pH 13, and pD 13), as detected by significant modifications of the coupled line-shape. Across the interfaces, we report a common rate constant (0.56 +/- 0.08 ps) and half rise (1.76 +/- 0.39 ps). This demonstrates that the reorganizational energy associated with solvent re-orientation is limited to affecting the ultrafast (400 fs) time resolution of the experiment characteristic of activation-less reactions and bond-reorganization. Furthermore, the formation kinetics are well-fit by a logistic function that describes an autocatalytic reaction and the surface population of titanium oxyl with excitation is well modelled by the Langevin equation. Both suggest that the invariant picosecond rise is due to a re-orientation of the titanium oxyl and its p-polarized vibrational dipole with respect to the strong Helmholtz electric field common to the probed interfaces.
ER -