2025/12/21 by Chenyu Wang, Wang, Chenyu, Wanjian Yin +3
Physics and Astronomy · Engineering · Chemistry · #Spectroscopy and Quantum Chemical Studies #Nanopore and Nanochannel Transport Studies #Electrostatics and Colloid Interactions
paper · doi:10.48550/arxiv.2512.18716
Water's ability to self-dissociate into H3O+ and OH- ions is central to acid-base chemistry and bioenergetics. Recent experimental advances have enabled the confinement of water down to the nanometre scale, even to the single-molecule limit, yet how this process is altered at the extreme nanoconfinement remains unclear. Using ab-initio calculations and enhanced-sampling machine-learning potential molecular dynamics, we show that monolayer-confined water exhibits a markedly lower barrier to auto-dissociation than bulk water. Confinement restructures both intramolecular bonding and the intermolecular hydrogen-bond network, while enforcing quasi-2D dipolar correlations that amplify dielectric fluctuations. Our results imply that two-dimensional confined water could act as a superdielectric medium and may exhibit superionic behavior, as observed in recent experiments. These findings reveal confinement as a powerful route to enhanced proton activity, shedding light on geochemical niches, biomolecular environments, and nanofluidic systems where water's chemistry is fundamentally reshaped.