First-principles study of water molecules at the electrified graphene surface

A detailed understanding of the atomic and electronic structures of electrified electrochemical interfaces has critical implications for the development of advanced energy conversion and storage devices. Here, graphene has been regarded as an ideal component for electrode materials due to its excellent mechanical, electrical, and chemical properties. Recently, for the improved understanding of electrified electrochemical interfaces, first-principles characterizations based on the approach combining density functional theory (DFT) and non-equilibrium Green’s function (NEGF) have been utilized with much successes. However, due to the requirement of semi-infinite electrodes, the DFT-NEGF approach so far could not be applied to graphene-based electrochemical interface models. In this presentation, taking the advantage of the multi-space constrained-search DFT (MS-DFT) formalism[1] that can handle the electrified finite electrodes, we firstly investigate the total enthalpy change of the water molecule on the electrified graphene electrode surface in a fully first-principles manner. Moreover, by carrying out nonequilibrium molecular dynamics simulations with MS-DFT, we show the bias-dependent configurations of water molecules at the electrified graphene-water interfaces. Comparing the interfacial water structures with those on metal electrodes, we extract important insight into the water at electrified electrochemical interfaces.

[1] J. Lee et al. Adv. Sci., 7, 2001038 (2020)