Disentangling Surface Charge and Electrolyte Effects on Interfacial Water at Electrified Pt(111)

Abstract

The structure of interfacial water at electrified metal electrodes is known to affect electrocatalysis, and experiments highlight its sensitivity to electrolyte ion identity and applied bias. To disentangle generic charge-controlled structural changes from ion-specific effects, we compare ab initio molecular dynamics water structures at electrified Pt(111) generated with two very different biasing schemes: an explicit ion imbalance in the double layer and homogeneously distributed partially charged hydrogen atoms. Despite these distinct counter-charge representations, both approaches yield a consistent average response of the first water bilayer, in particular of the chemisorbed first layer, when compared on a common surface-charge scale. Method-dependent differences, in particular those associated with explicit electrolyte ions, become apparent only in more local structural descriptors. The hydrogen-bond topology reveals charge-dependent chain-to-ring rearrangements, with explicit ions enhancing ring populations near the potential of zero charge. Layer-resolved vibrational density of states (VDOS) assigns the strongest O-H stretching perturbation to chemisorbed first-layer water and identifies high-frequency signatures of ion-coordinated water, while computed vibrational sum-frequency generation (VSFG) spectra show that the physisorbed, electrolyte-facing region is particularly sensitive to the counter-charge representation. These results suggest that surface charge controls the average structural response, whereas electrolyte ions and their solvation shells become visible only when locally refined descriptors are investigated or probed, e.g. the H-bond network topology and vibrational fingerprints of the interfacial bilayer.

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Cite

BibTeX RIS

BibTeX

@misc{eggert2026disentangling,
  title = {{Disentangling Surface Charge and Electrolyte Effects on Interfacial Water at Electrified Pt(111)}},
  author = {Thorben Eggert and Lang Li and Yair Litman and Karsten Reuter and Nicolas G. Hoermann and Clotilde S. Cucinotta},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.26685},
  eprint = {2609.26685},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.26685},
  note = {CC BY 4.0},
}

RIS

TY  - UNPB
TI  - Disentangling Surface Charge and Electrolyte Effects on Interfacial Water at Electrified Pt(111)
AU  - Thorben Eggert
AU  - Lang Li
AU  - Yair Litman
AU  - Karsten Reuter
AU  - Nicolas G. Hoermann
AU  - Clotilde S. Cucinotta
PY  - 2026
DA  - 2026/09/22
PB  - arXiv
DO  - 10.48550/arxiv.2609.26685
UR  - https://arxiv.org/abs/2609.26685
AB  - The structure of interfacial water at electrified metal electrodes is known to affect electrocatalysis, and experiments highlight its sensitivity to electrolyte ion identity and applied bias. To disentangle generic charge-controlled structural changes from ion-specific effects, we compare ab initio molecular dynamics water structures at electrified Pt(111) generated with two very different biasing schemes: an explicit ion imbalance in the double layer and homogeneously distributed partially charged hydrogen atoms. Despite these distinct counter-charge representations, both approaches yield a consistent average response of the first water bilayer, in particular of the chemisorbed first layer, when compared on a common surface-charge scale. Method-dependent differences, in particular those associated with explicit electrolyte ions, become apparent only in more local structural descriptors. The hydrogen-bond topology reveals charge-dependent chain-to-ring rearrangements, with explicit ions enhancing ring populations near the potential of zero charge. Layer-resolved vibrational density of states (VDOS) assigns the strongest O-H stretching perturbation to chemisorbed first-layer water and identifies high-frequency signatures of ion-coordinated water, while computed vibrational sum-frequency generation (VSFG) spectra show that the physisorbed, electrolyte-facing region is particularly sensitive to the counter-charge representation. These results suggest that surface charge controls the average structural response, whereas electrolyte ions and their solvation shells become visible only when locally refined descriptors are investigated or probed, e.g. the H-bond network topology and vibrational fingerprints of the interfacial bilayer.
ER  -

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