Unveiling the Angstrom-Scale Interfacial Electron Spillover through the Metal/Electrolyte Interface

The behaviors of solid-liquid interfacial electron spillovers under negative potentials are crucial for understanding heterogeneous reactions and catalysts. The missing experimental details at the angstrom scale leave the current understanding of interfacial electron spillovers largely conceptual. Herein, we demonstrated interfacial electron spillover at electrode-electrolyte interfaces by combining in situ electrochemical plasmon-enhanced Raman spectroscopy (PERS) with a plasmonic molecular ruler strategy. Using a series of molecules adsorbed on or proximate to metallic electrodes (Pt, Pd, Au, and Ag) as molecular rulers, the electron spillover from electrodes to electrolytes was experimentally and theoretically correlated to the PERS bands of the functional groups of rulers, which provided a spatial resolution down to the angstrom scale. The electron spillover length was highly dependent on the potentials, metals, and electrolytes. An electron spillover with a length of up to 4 Å was observed at the Ag electrode-organic electrolyte interface. These results provide quantitative measurements of the fundamental details of electronic behaviors in metal-liquid interfaces, which may guide efforts to tailor the physical and chemical properties of metals under electrochemical polarization and prospectively enable active control of quantum plasmonics for angstrom-scale interfacial sensing.