An understanding of the solution-crystal interface that connects the actual molecular structures to the macroscopic properties, was obtained, by combining in situ synchrotron X-ray measurements on submerged rutile single crystal surfaces with ab inito calculations, molecular dynamic simulations, and macroscopic ion adsorption data. All X-ray, ab inito, molecular dynamics, and ion adsorption results were broadly compatible with a Stern-based description of EDL structure. All cations were found to be adsorbed as 'inner sphere' species bonded directly to surface oxygen atoms. A link between macroscopic manifestations of metal oxide surface charging and ion adsorption and the molecule-scale interfacial structures was established.