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Peer-reviewedCC BYJournal of the American Chemical Society

Interfacial pH Dynamics in Lattice-Nitrogen Protonation to Ammonia.

  • David Kumar Yesudoss1
  • Joshua Ferguson1
  • Anabela Meier2
  • Abdoulaye Djire1,3
  1. 1Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, Texas77843, United States.
  2. 2Department of Chemistry, Texas A&M University, College Station, Texas77843, United States.
  3. 3Department of Materials Science and Engineering, Texas A&M University, College Station, Texas77843, United States.
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Abstract

We recently discovered a new class of nitride MXenes (MNenes) that undergo lattice-nitrogen protonation to form ammonia under cathodic potentials. Unexpectedly, neutral electrolytes outperform both acidic and alkaline media, revealing the critical role of the interfacial proton environment in the formation of ammonia. However, how dynamic interfacial pH governs this mechanism remains poorly understood, because conventional ex situ characterization cannot probe local pH under operating conditions. Here, we develop an in-house in situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy with phosphate speciation as a vibrational pH reporter to monitor in real time the interfacial pH near the Ti2NTx MNene catalyst during cathodic polarization. On one hand, we found that in a nominally neutral phosphate buffer, cathodic operation drives the Ti2NTx interface strongly alkaline despite the fact that the bulk remains neutral, whereas a mildly acidic electrolyte partially moderates this pH rise by increasing proton availability. On the other hand, a strongly acidic electrolyte minimizes interfacial pH changes but can also promote non-catalytic lattice-nitrogen protonation and release of NH3. Time-dependent measurements show that interfacial pH is governed by the balance between current-driven alkalinity generation and electrolyte-mediated neutralization. Overall, this in situ study shows that electrolyte pH and current density must be tuned together to maintain a fairly neutral interfacial environment favorable for lattice-nitrogen protonation to ammonia.

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Cite

BibTeXRIS
BibTeX
@article{yesudoss2026interfacial,
  title = {{Interfacial pH Dynamics in Lattice-Nitrogen Protonation to Ammonia.}},
  author = {David Kumar Yesudoss and Joshua Ferguson and Anabela Meier and Abdoulaye Djire},
  journal = {Journal of the American Chemical Society},
  year = {2026},
  month = oct,
  doi = {10.1021/jacs.6c14168},
  url = {https://europepmc.org/article/MED/42912296},
  note = {CC BY},
}
RIS
TY  - JOUR
TI  - Interfacial pH Dynamics in Lattice-Nitrogen Protonation to Ammonia.
AU  - David Kumar Yesudoss
AU  - Joshua Ferguson
AU  - Anabela Meier
AU  - Abdoulaye Djire
PY  - 2026
DA  - 2026/10/01
JO  - Journal of the American Chemical Society
DO  - 10.1021/jacs.6c14168
UR  - https://europepmc.org/article/MED/42912296
AB  - We recently discovered a new class of nitride MXenes (MNenes) that undergo lattice-nitrogen protonation to form ammonia under cathodic potentials. Unexpectedly, neutral electrolytes outperform both acidic and alkaline media, revealing the critical role of the interfacial proton environment in the formation of ammonia. However, how dynamic interfacial pH governs this mechanism remains poorly understood, because conventional ex situ characterization cannot probe local pH under operating conditions. Here, we develop an in-house in situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy with phosphate speciation as a vibrational pH reporter to monitor in real time the interfacial pH near the Ti2NTx MNene catalyst during cathodic polarization. On one hand, we found that in a nominally neutral phosphate buffer, cathodic operation drives the Ti2NTx interface strongly alkaline despite the fact that the bulk remains neutral, whereas a mildly acidic electrolyte partially moderates this pH rise by increasing proton availability. On the other hand, a strongly acidic electrolyte minimizes interfacial pH changes but can also promote non-catalytic lattice-nitrogen protonation and release of NH3. Time-dependent measurements show that interfacial pH is governed by the balance between current-driven alkalinity generation and electrolyte-mediated neutralization. Overall, this in situ study shows that electrolyte pH and current density must be tuned together to maintain a fairly neutral interfacial environment favorable for lattice-nitrogen protonation to ammonia.
SN  - 0002-7863
SN  - 1520-5126
ER  -