First-principles study of the hydrogen-bonding network in water at the biased electrode interface

A crucial step for the development of next-generation electrochemical devices will be the understanding of the atomic and electronic structures of interfacial waters next to biased electrode surfaces. In this presentation, carrying out first-principles non-equilibrium electronic structure calculation within the multi-space constrained-search density functional theory (MS-DFT) formalism we have recently developed, we study the bias-dependent structural and electronic properties of the hydrogen-bonding network of water molecules at the gold electrode interface. Benchmarking the non-equilibrium force profile of a single water molecule next to the gold electrode obtained from non-equilibrium Green’s function (NEGF) calculations, we confirm the practical equivalence between MS-DFT and DFT-NEGF. We also report the advantages of MS-DFT in view of electrochemical device simulations by providing (1) well-defined binding energies and (2) the electrochemical potential profiles. Analyzing the spatial profiles of the electrochemical potentials or quasi-Fermi levels at the gold-water interface at varying bias voltages, we extract several important insights into the nature of hydrogen bond network of liquid water at the biased electrochemical interfaces.