2026
Yixuan Feng, Xavier R. Advincula, Hongwei Fang, Christoph Schran
Clay edges are dynamic proton-conducting networks modulated by structure and pH Journal Article
In: J. Phys. Chem. Lett., vol. 17, iss. 9, pp. 2679–2688, 2026.
Abstract | Links | BibTeX | Tags: Charge Transfer, Chemical Reactivity, Ions in Water, Water, Water at Interfaces
@article{Feng2026/10.1021/acs.jpclett.5c03748,
title = {Clay edges are dynamic proton-conducting networks modulated by structure and pH},
author = {Yixuan Feng and Xavier R. Advincula and Hongwei Fang and Christoph Schran},
url = {https://pubs.acs.org/doi/full/10.1021/acs.jpclett.5c03748},
doi = {10.1021/acs.jpclett.5c03748},
year = {2026},
date = {2026-02-22},
urldate = {2026-02-22},
journal = {J. Phys. Chem. Lett.},
volume = {17},
issue = {9},
pages = {2679–2688},
abstract = {Montmorillonite, a ubiquitous clay mineral, plays a vital role in geochemical and environmental processes due to its chemically complex edge surfaces. However, the molecular-scale acid-base reactivity of these interfaces remains poorly understood due to the limitations of both experimental resolution and conventional simulations. Here, we employ machine learning potentials with first-principles accuracy to perform nanosecond-scale molecular dynamics simulations of montmorillonite nanoparticles across a range of pH. Our results reveal clear amphoteric behavior, with edge sites undergoing protonation in acidic environments and deprotonation in basic conditions, accompanied by pH-dependent surface charge regulation. Even at neutral pH, spontaneous and directional proton transfer events are common, proceeding via both direct and solvent-mediated pathways. These findings demonstrate that montmorillonite edges are not static arrays of hydroxyl groups but dynamic, proton-conducting networks whose reactivity and charge state are modulated by local structure and solution conditions. This work offers a molecular-level framework for understanding proton transport and buffering in clay-water systems, with broad implications for catalysis, ion exchange, and environmental remediation.},
keywords = {Charge Transfer, Chemical Reactivity, Ions in Water, Water, Water at Interfaces},
pubstate = {published},
tppubtype = {article}
}
Montmorillonite, a ubiquitous clay mineral, plays a vital role in geochemical and environmental processes due to its chemically complex edge surfaces. However, the molecular-scale acid-base reactivity of these interfaces remains poorly understood due to the limitations of both experimental resolution and conventional simulations. Here, we employ machine learning potentials with first-principles accuracy to perform nanosecond-scale molecular dynamics simulations of montmorillonite nanoparticles across a range of pH. Our results reveal clear amphoteric behavior, with edge sites undergoing protonation in acidic environments and deprotonation in basic conditions, accompanied by pH-dependent surface charge regulation. Even at neutral pH, spontaneous and directional proton transfer events are common, proceeding via both direct and solvent-mediated pathways. These findings demonstrate that montmorillonite edges are not static arrays of hydroxyl groups but dynamic, proton-conducting networks whose reactivity and charge state are modulated by local structure and solution conditions. This work offers a molecular-level framework for understanding proton transport and buffering in clay-water systems, with broad implications for catalysis, ion exchange, and environmental remediation.
2025
Zeke Coady, Samuel G.H. Brookes, Zhaohan Shen, Benjamin J. Rhodes, Grace Mapstone, Zhen Xu, Wei Yu, Hirotomo Nishihara, Christoph Schran, Angelos Michaelides, Alexander C. Forse
Unexpected oversolubility of CO$_2$ measured at electrode–electrolyte interfaces Journal Article
In: J. Am. Chem. Soc., vol. 147, iss. 40, pp. 36310–36319, 2025.
Abstract | Links | BibTeX | Tags: Chemical Reactivity, Machine Learning Potentials, Water at Interfaces
@article{Coady2025/10.1021/jacs.5c09712,
title = {Unexpected oversolubility of CO$_2$ measured at electrode–electrolyte interfaces},
author = {Zeke Coady and Samuel G.H. Brookes and Zhaohan Shen and Benjamin J. Rhodes and Grace Mapstone and Zhen Xu and Wei Yu and Hirotomo Nishihara and Christoph Schran and Angelos Michaelides and Alexander C. Forse},
url = {https://pubs.acs.org/doi/full/10.1021/jacs.5c09712},
doi = {10.1021/jacs.5c09712},
year = {2025},
date = {2025-09-23},
urldate = {2025-09-23},
journal = {J. Am. Chem. Soc.},
volume = {147},
issue = {40},
pages = {36310–36319},
abstract = {Enhancements in gas solubility in pore-confined liquids─termed oversolubility─can drastically influence gas separation and catalytic efficiency in confined environments; however, they remain poorly understood in electrochemical $CO_2$ capture and reduction systems. While previous investigations of oversolubility have emphasized the importance of mesoporosity and incomplete pore saturation by the solvent, in this work, we report an unprecedented 30-fold oversolubility effect for $CO_2$ in solely microporous activated carbons saturated with 1 M $Na_2SO_{4(aq)}$. The oversolubility effect occurs regardless of the activated carbon’s functional groups and level of disorder and is enhanced for smaller pore sizes. Oversolubility is quantified using solid-state $^{13}C$ nuclear magnetic resonance spectroscopy (NMR), enabling differentiation between in-pore and ex-pore $CO_2$ and $HCO_3^–$. Atomistic modeling of the system, based on a machine-learning model delivering first-principles accuracy, suggests that the effect is driven by an adsorption-like mechanism underpinned by favorable interactions between $CO_2$ and the pore walls. Our findings demonstrate the unexpected importance of oversolubility for gas uptake in microporous, solvent-saturated carbon electrodes, an effect with direct relevance for improving electrochemical $CO_2$ capture and conversion technologies.},
keywords = {Chemical Reactivity, Machine Learning Potentials, Water at Interfaces},
pubstate = {published},
tppubtype = {article}
}
Enhancements in gas solubility in pore-confined liquids─termed oversolubility─can drastically influence gas separation and catalytic efficiency in confined environments; however, they remain poorly understood in electrochemical $CO_2$ capture and reduction systems. While previous investigations of oversolubility have emphasized the importance of mesoporosity and incomplete pore saturation by the solvent, in this work, we report an unprecedented 30-fold oversolubility effect for $CO_2$ in solely microporous activated carbons saturated with 1 M $Na_2SO_{4(aq)}$. The oversolubility effect occurs regardless of the activated carbon’s functional groups and level of disorder and is enhanced for smaller pore sizes. Oversolubility is quantified using solid-state $^{13}C$ nuclear magnetic resonance spectroscopy (NMR), enabling differentiation between in-pore and ex-pore $CO_2$ and $HCO_3^–$. Atomistic modeling of the system, based on a machine-learning model delivering first-principles accuracy, suggests that the effect is driven by an adsorption-like mechanism underpinned by favorable interactions between $CO_2$ and the pore walls. Our findings demonstrate the unexpected importance of oversolubility for gas uptake in microporous, solvent-saturated carbon electrodes, an effect with direct relevance for improving electrochemical $CO_2$ capture and conversion technologies.
Samuel G.H. Brookes, Venkat Kapil, Angelos Michaelides, Christoph Schran
CO$_2$ hydration at the air–water interface: A surface-mediated “in-and-out” mechanism Journal Article
In: Proc. Natl. Acad. Sci., vol. 122, no. 34, pp. e2502684122, 2025.
Abstract | Links | BibTeX | Tags: Chemical Reactivity, Machine Learning Potentials, Water at Interfaces
@article{Brookes2025/10.1073/pnas.2502684122,
title = {CO$_2$ hydration at the air–water interface: A surface-mediated “in-and-out” mechanism},
author = {Samuel G.H. Brookes and Venkat Kapil and Angelos Michaelides and Christoph Schran},
url = {https://www.pnas.org/doi/full/10.1073/pnas.2502684122},
doi = {10.1073/pnas.2502684122},
year = {2025},
date = {2025-08-20},
urldate = {2025-08-20},
journal = {Proc. Natl. Acad. Sci.},
volume = {122},
number = {34},
pages = {e2502684122},
abstract = {An understanding of the $CO_2 + H_2O$ hydration reaction is crucial for modeling the effects of ocean acidification, for enabling novel carbon storage solutions, and as a model process in the geosciences. While the mechanism of this reaction has been investigated extensively in the condensed phase, its mechanism at the air–water interface remains elusive, leaving uncertain the contribution that surface-adsorbed $CO_2$ makes to the overall acidification reaction. In this study, we employ machine-learned potentials trained to various levels of theory to provide a molecular-level understanding of $CO_2$ hydration at the air–water interface. We show that reaction at the interface follows a surface-mediated “in-and-out” mechanism: $CO_2$ diffuses into the aqueous surface layer, reacts to form carbonic acid, and is subsequently expelled from solution. We show that this surface layer provides a bulk-like solvation environment, engendering similar modes of reactivity and near-identical free energy profiles for the bulk and interfacial processes. Our study unveils an unconventional reaction mechanism that underscores the dynamic nature of the molecular reaction site at the air–water interface. The similarity between bulk and interfacial profiles shows that $CO_2$ hydration is equally as feasible under these two solvation environments and that acidification rates are likely enhanced by this additional surface contribution.},
keywords = {Chemical Reactivity, Machine Learning Potentials, Water at Interfaces},
pubstate = {published},
tppubtype = {article}
}
An understanding of the $CO_2 + H_2O$ hydration reaction is crucial for modeling the effects of ocean acidification, for enabling novel carbon storage solutions, and as a model process in the geosciences. While the mechanism of this reaction has been investigated extensively in the condensed phase, its mechanism at the air–water interface remains elusive, leaving uncertain the contribution that surface-adsorbed $CO_2$ makes to the overall acidification reaction. In this study, we employ machine-learned potentials trained to various levels of theory to provide a molecular-level understanding of $CO_2$ hydration at the air–water interface. We show that reaction at the interface follows a surface-mediated “in-and-out” mechanism: $CO_2$ diffuses into the aqueous surface layer, reacts to form carbonic acid, and is subsequently expelled from solution. We show that this surface layer provides a bulk-like solvation environment, engendering similar modes of reactivity and near-identical free energy profiles for the bulk and interfacial processes. Our study unveils an unconventional reaction mechanism that underscores the dynamic nature of the molecular reaction site at the air–water interface. The similarity between bulk and interfacial profiles shows that $CO_2$ hydration is equally as feasible under these two solvation environments and that acidification rates are likely enhanced by this additional surface contribution.