Polarization induced water molecule dissociation below the first-order electronic-phase transition temperature

TL;DR

This study demonstrates that polarization effects induce water molecule dissociation on MgO surfaces below a certain electronic-phase transition temperature, highlighting the role of asymmetric bond polarizabilities and substrate interactions.

Contribution

It provides direct evidence linking polarization-induced bond shifts to water splitting on MgO, revealing a novel dissociation mechanism influenced by temperature and substrate effects.

Findings

Existence of blue- and red-shifting O-H bonds in adsorbed water

Weaker H-O bond near surface compensates with a stronger bond

Polarizability changes drive water dissociation below a phase transition

Abstract

Hydrogen produced from the photocatalytic splitting of water is one of the reliable alternatives to replace the polluting fossil and the radioactive nuclear fuels. Here, we provide unequivocal evidence for the existence of blue- and red-shifting O$-$H covalent bonds within a single water molecule adsorbed on MgO surface as a result of asymmetric displacement polarizabilities. The adsorbed H-O-H on MgO gives rise to one weaker H-O bond, while the other O-H covalent bond from the same adsorbed water molecule compensates this effect with a stronger bond. The weaker bond (nearest to the surface), the interlayer tunneling electrons and the silver substrate are shown to be the causes for the smallest dissociative activation energy on MgO monolayer. The origin that is responsible to initiate the splitting mechanism is proven to be due to the changes in the polarizability of an adsorbed water molecule, which are further supported by the temperature-dependent static dielectric constant measurements for water below the first-order electronic-phase transition temperature.