Nuclear quantum effects amplify autoionization-driven superionic behaviour in nanoconfined monolayer water

While nuclear quantum effects influence autoionization in ambient-condition bulk water, their impact on autoionization-driven phase transitions is only observed at extreme conditions (in the range of many tens or hundreds of GPa). Here, we show that, for a monolayer of water in uniform nanoconfinement, nuclear quantum effects induce a superionic phase transition under milder conditions than in bulk. Our calculations suggest that this effect brings superionic behaviour into pressure regimes much closer to those accessible in current 2D-material-water encapsulation experiments.