Structural, dynamical and dielectric properties of water in contact with TiO2 surfaces via molecular-dynamics simulations

Abstract

Undoubtedly, enhancing our knowledge of the dielectric response, structural, translational-librational and dynamics properties of water either in bulk environment or in its interfacial guise are required to provide a detailed understanding of the fundamental properties crucial for the development of more efficient and improved control of photo-energy conversion devices, especially those based on photo-electrochemical (PEC) water splitting. To this end, classical equilibrium molecular-dynamics simulations have been performed to rationalise the intriguing behaviour of bulk water and, in particular, interfacial hydration water layers with both rutile (110) and anatase (101) surfaces of titanium dioxide (TiO2). The dielectric characteristics of interfacial water in the first-adsorbed water layer evince a markedly reduced value in comparison to the bulk water environment, as well as lower self-diffusivity (owing to surface-confinement effects). In addition, this work presents evidence describing behavioural pattern of adsorbed hydration layers which reflects similarities observed in the underlying surface-identity mechanism of titania slabs used, and on how surface atomistic architecture – indeed, ‘surface personality’ – dictates to a large extent the dielectric ‘matching’ of hydration-water layers adsorbed thereon. Further analyses show evidence of strong-roles underpinning the hydrogen-bond network at the water/titania interfaces.