Fig. 2: Time-dependent evolution of HOPG/aqueous solution interfaces at OCP.
From: Probing the molecular structure at graphite–water interfaces by correlating 3D-AFM and SHINERS
a 3D-AFM x–z force maps of an HOPG/pure water interface obtained at the beginning of the measurement and after 60 min (conducted in Madrid). Scale bars: 1 nm (x and z directions). b Force–distance curves of HOPG/pure water (extracted from (a)) and HOPG/aqueous solutions interfaces, at the beginning of the experiment and after 1–1.5 h (Madrid). Individual curves are shown in gray, and average curves in blue. The interlayer distance d12 is marked on each set of curves. c SHINERS spectra of an HOPG/0.1 M K2SO4 solution interface at the beginning (t = 0 min) and after 132 min across three spectral regions: fingerprint (FP), C–H stretching (νCH), and O–H stretching (νOH). The νOH band is deconvoluted into five individual Voigt peaks, OH-1 (red), OH-2 (blue), OH-3 (green), OH-4 (orange), and OH-5 (violet). The sum of the fits is shown in pink. d Time evolution of the peak areas for FP, νCH, and νOH modes. e, f Peak positions and area fractions of the individual νOH peaks for t = 0 and 132 min. g Schematic diagrams of the time-dependent evolution of HOPG–water interfaces at OCP, depicting the replacement of interfacial water by adventitious hydrocarbons and associated changes in the hydrogen-bonding environment—specifically, an increase in the fractions of OH-1 and OH-2, a decrease in the fraction of OH-3, and the disappearance of OH-4 and OH-5 configurations. Source data are provided as a Source Data file.
