Characterizing surface-confined interfacial water at graphene surface by in situ Raman spectroscopy

Summary

The surface-confined interfacial water at graphene exhibits highly localized changes in applied electric fields, thus playing an important role in energy-related fields. However, detecting the unique signals from surface-confined interfacial water located at the two-phase boundary is notoriously difficult owing to the complex and confined environment. This difficulty is compounded further when studying surface-confined interfacial water on atom-thick graphene surfaces. Now, by assembling graphene at atomically ordered Au(111) single-crystal surfaces, we utilize in situ Raman spectroscopy and ab initio molecular dynamics simulations to characterize the surface-confined interfacial water on graphene. Interfacial water predominantly consists of hydrogen-bonded or cation-coordinating water molecules. Dynamic potential-dependent transformations in the water structure are directly observed, whereby water changes from a parallel configuration to a one-H down and then to a two-H down structure. These results are an essential step toward understanding the fundamental processes of surface-confined interfacial water at graphene surfaces and guiding the design of an efficient electrocatalytic interface.