Fig. 4: Hydrogen bonding in 2D confinement.
From: Vibrational signature of hydrated protons confined in MXene interlayers
a Radial distribution function of non-covalently bonded OA-HD distances between a hydronium ion and its four nearest-neighbour water molecules (solid lines) and the resulting coordination numbers of the hydronium ion (dashed lines) in bulk water with 0.05 H+ per H2O (black), MXene-confined water at low [H+] (Ti3C2O2·1.42H2O·0.08H, red), and MXene confined water at high [H+] (Ti3C2O2·1.42H2O·0.25H, blue). The vertical dotted line represents the hydrogen bond length cutoff at 2.5 Å. The coordination numbers at this O–H distance are marked in the figure. Inset: Hydronium ion with 4 nearest water molecules; the H-bonds are marked by dashed lines. b Fully H-bonded hydronium ion in bulk water. c Schematic representation of the effect of 2D confinement on proton hydration.
