Long-Range Redox and Water Activation at Metal–Water Interfaces with Ferroelectric Ordering

The molecular structure of water has profound influence on electron transfer and redox processes at metal-water interfaces. While ab initio molecular dynamics simulations provide an accurate description of the interfacial structure, the respective computational cost is often prohibitive. Static simulations using a few ordered water layers can serve as a pragmatic alternative maintaining an explicit description of molecular interactions at an affordable computational cost. We here study the coupling between electronic and structural degrees of freedom at ferroelectrically ordered metal-water interfaces. With increasing number of ice-like water layers, we observe a long-range transfer of electrons between the metal's Fermi level and HOMO/LUMO states of the outermost water molecules, mediated by ordered solvent dipole layers. Our findings reveal limitations of the applicability of the ordered interface model and reveal a strong coupling between ferroelectric ordering and long-range (auto)redox phenomena at dipolar solvent structures, shedding new light onto the long-standing question on the existence and stability of ferroelectric ice. Implications for the activation of water molecules in electrocatalytic reactions at charged metal-water interfaces are suggested.