Water on silicene: A hydrogen bond-autocatalyzed physisorption-chemisorption-dissociation transition

摘要

A single water molecule is nothing special.However,macroscopic water displays many anomalous properties at interfaces,such as hydrophobicity and hydrophilicity.Although the underlying mechanisms remain elusive,hydrogen bonds between water molecules are expected to play a major role in these interesting phenomena.An important question concerns whether water clusters containing few molecules are qualitatively different from a single molecule.Using the water adsorption behavior as an example and by carefully choosing two-dimensional silicene as the substrate material,we demonstrate that water monomers,dimers,and trimers show distinct adsorption properties at the substrate surface.On silicene,the additional water molecules in dimers and trimers induce a transition from physisorption to chemisorption and then to dissociation,arising from the enhancement of charge transfer and proton transfer processes induced by hydrogen bonding.Such a hydrogen bond autocatalytic effect is expected to have broad applications in metal-free catalysis for the oxygen reduction reaction and water dissociation.