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PreprintCC BYChemRxiv

Localizing and quantifying the dynamic interfacial proton population in alkaline electrocatalysis

  • Xinwei Zhu
  • Daniel Ohm1
  • Qiqi Yang1
  • Adrian Heinritz2
  • Paramaconi Rodriguez3
  • Xiaomin Liu1
  • Tobias Binninger4,5
  • Katrin F. Domke4,5
5 affiliations
  1. 1Molecular Spectroscopy Group, Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz, Germany, 55128
  2. 2PSI Center for Energy & Environmental Sciences, Paul Scherrer Institute, Villigen PSI, Switzerland, CH-5232
  3. 3CIC energiGUNE,, C/Albert Einstein, 48, Vitoria-Gasteiz (Álava, Spain, 01510
  4. 4Theory and Computation of Energy Materials (IET-3), Institute of Energy Technologies, Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Straße, Jülich, Germany, 52425
  5. 5Faculty of Chemistry, Chair of Physical Chemistry II, University of Duisburg-Essen, Universitätsstr. 5, Essen, Germany, 45141
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Abstract

In alkaline electrocatalysis, electrostatic theory predicts, and experiments confirm, interfacial acidity that deviates from bulk pHb. The location and magnitude of the proton population within the electric double layer (EDL) and its evolution with catalytic turnover have remained unresolved, leaving a critical gap for mechanistic interpretation across proton-coupled electrocatalysis. Here, using showcase alkaline (pHb 13) hydrogen evolution on Au, electrochemical fluorescence microscopy combined with electrostatic modelling demonstrates an apparent interfacial pH inversion of more than eight units within 1 nm of 1 the electrode, below the outer Helmholtz plane. This EDL proton population is dynamic. At hydrogen-evolution onset, the reaction can draw from it. As electrocatalytic turnover increases, H+ consumption outpaces its electrostatic replenishment, favouring a water-based reaction pathway. Localizing and quantifying this dynamic proton population closes a key gap in the mechanistic interpretation of alkaline hydrogen evolution with a proton-availability framework likely relevant to alkaline electrocatalysis and electrosynthesis at large.

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Cite

BibTeXRIS
BibTeX
@misc{zhu2026localizing,
  title = {{Localizing and quantifying the dynamic interfacial proton population in alkaline electrocatalysis}},
  author = {Xinwei Zhu and Daniel Ohm and Qiqi Yang and Adrian Heinritz and Paramaconi Rodriguez and Xiaomin Liu and Tobias Binninger and Katrin F. Domke},
  howpublished = {ChemRxiv},
  year = {2026},
  month = sep,
  doi = {10.26434/chemrxiv.15009338/v1},
  url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009338/v1},
  note = {CC BY},
}
RIS
TY  - UNPB
TI  - Localizing and quantifying the dynamic interfacial proton population in alkaline electrocatalysis
AU  - Xinwei Zhu
AU  - Daniel Ohm
AU  - Qiqi Yang
AU  - Adrian Heinritz
AU  - Paramaconi Rodriguez
AU  - Xiaomin Liu
AU  - Tobias Binninger
AU  - Katrin F. Domke
PY  - 2026
DA  - 2026/09/23
PB  - ChemRxiv
DO  - 10.26434/chemrxiv.15009338/v1
UR  - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009338/v1
AB  - In alkaline electrocatalysis, electrostatic theory predicts, and experiments confirm, interfacial acidity that deviates from bulk pHb. The location and magnitude of the proton population within the electric double layer (EDL) and its evolution with catalytic turnover have remained unresolved, leaving a critical gap for mechanistic interpretation across proton-coupled electrocatalysis. Here, using showcase alkaline (pHb 13) hydrogen evolution on Au, electrochemical fluorescence microscopy combined with electrostatic modelling demonstrates an apparent interfacial pH inversion of more than eight units within 1 nm of 1 the electrode, below the outer Helmholtz plane. This EDL proton population is dynamic. At hydrogen-evolution onset, the reaction can draw from it. As electrocatalytic turnover increases, H+ consumption outpaces its electrostatic replenishment, favouring a water-based reaction pathway. Localizing and quantifying this dynamic proton population closes a key gap in the mechanistic interpretation of alkaline hydrogen evolution with a proton-availability framework likely relevant to alkaline electrocatalysis and electrosynthesis at large.
ER  -