Reaction-orthogonal solid-state reference enables potentiometric studies of vapor phase thermochemical catalysis
- 1Department of Chemistry
- 2Massachusetts Institute of Technology
- 3Department of Chemical Engineering
Abstract
Electrochemical mechanisms have been shown to be operative in the catalysis of numerous thermochemical redox reactions. These mechanisms have been elucidated by the measurement of the electrochemical potential of the catalyst during turnover (E cat ). A rich array of electrochemical tools allows for measurement of E cat during liquid-phase catalysis, but these are ill-suited to E cat measurements in higher temperature vapor-phase catalysis. Herein we report a solid electrolyte potentiometry (SEP) methodology that employs a Na β″-alumina solid electrolyte to measure E cat relative to the Na/Na + reference couple. As Na + is not typically a reactant or product in (electro)catalytic reactions, this reference is reaction-orthogonal, providing a common reference value for E cat measurement and analysis across diverse reaction classes and environments. Reaction-orthogonal SEP (RO-SEP) of Pt/C under H 2 enables measurement of the H 2 /H + equilibrium potential in the vapor phase across a wide temperature range from ambient to 325 °C. We find that promoting salts establish vapor phase proton activities comparable to their values in bulk aqueous medium, at ambient temperature. We apply RO-SEP to study the Au/C-catalyzed aerobic oxidation of 2-propanol to acetone and find that the catalyst is spontaneously and differentially polarized as a function of O 2 pressure under vapor phase reaction conditions. Simultaneous measurement of rate and E cat reveals a rate-potential scaling for vapor phase aerobic IPA oxidation that parallels that of liquid phase electrolytic IPA oxidation, suggesting a shared electrochemical mechanism between the two conditions. Lastly, H 2 /H + potentiometry reveals that alkali promoters in this reaction act principally via increasing the pH at the catalyst surface, which in turn enhances the kinetics of both the oxygen reduction and 2-propanol oxidation half-reaction. This reaction-orthogonal methodology for quantifying E cat enables broad-based investigations into the role of charge transfer in vapor phase heterogeneous catalysis.
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BibTeX
@misc{harraz2026reactionorthogonal,
title = {{Reaction-orthogonal solid-state reference enables potentiometric studies of vapor phase thermochemical catalysis}},
author = {Deiaa M. Harraz and Cole S. Cadaram and Kunal M. Lodaya and Bryan Y. Tang and Yogesh Surendranath},
howpublished = {ChemRxiv},
year = {2026},
month = sep,
doi = {10.26434/chemrxiv.15002247/v2},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15002247/v2},
note = {CC BY},
}
RIS
TY - UNPB
TI - Reaction-orthogonal solid-state reference enables potentiometric studies of vapor phase thermochemical catalysis
AU - Deiaa M. Harraz
AU - Cole S. Cadaram
AU - Kunal M. Lodaya
AU - Bryan Y. Tang
AU - Yogesh Surendranath
PY - 2026
DA - 2026/09/10
PB - ChemRxiv
DO - 10.26434/chemrxiv.15002247/v2
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15002247/v2
AB - Electrochemical mechanisms have been shown to be operative in the catalysis of numerous thermochemical redox reactions. These mechanisms have been elucidated by the measurement of the electrochemical potential of the catalyst during turnover (E cat ). A rich array of electrochemical tools allows for measurement of E cat during liquid-phase catalysis, but these are ill-suited to E cat measurements in higher temperature vapor-phase catalysis. Herein we report a solid electrolyte potentiometry (SEP) methodology that employs a Na β″-alumina solid electrolyte to measure E cat relative to the Na/Na + reference couple. As Na + is not typically a reactant or product in (electro)catalytic reactions, this reference is reaction-orthogonal, providing a common reference value for E cat measurement and analysis across diverse reaction classes and environments. Reaction-orthogonal SEP (RO-SEP) of Pt/C under H 2 enables measurement of the H 2 /H + equilibrium potential in the vapor phase across a wide temperature range from ambient to 325 °C. We find that promoting salts establish vapor phase proton activities comparable to their values in bulk aqueous medium, at ambient temperature. We apply RO-SEP to study the Au/C-catalyzed aerobic oxidation of 2-propanol to acetone and find that the catalyst is spontaneously and differentially polarized as a function of O 2 pressure under vapor phase reaction conditions. Simultaneous measurement of rate and E cat reveals a rate-potential scaling for vapor phase aerobic IPA oxidation that parallels that of liquid phase electrolytic IPA oxidation, suggesting a shared electrochemical mechanism between the two conditions. Lastly, H 2 /H + potentiometry reveals that alkali promoters in this reaction act principally via increasing the pH at the catalyst surface, which in turn enhances the kinetics of both the oxygen reduction and 2-propanol oxidation half-reaction. This reaction-orthogonal methodology for quantifying E cat enables broad-based investigations into the role of charge transfer in vapor phase heterogeneous catalysis.
ER -