Exploring Electrochemical Double Layer Formation and Dynamics with Surface Plasmon Resonance Grating Structures

Voltage-induced changes in the electric double layer (EDL) are essential in electrochemical reactions, influenced by local ion concentration and electric fields near electrodes. Techniques such as second harmonic generation (SHG) spectroscopy [1-5], ATR-FTIR spectroscopy [6], SEIRAS [7], and SERS spectroscopy [8] have been used to examine these properties. We introduce a method using surface plasmon resonance (SPR) with metal gratings to investigate EDL behavior at electrode/electrolyte interfaces. This method detects shifts in the grating’s resonant angle (Δφ), linked to local refractive index changes (Δn_local) with a resolution of Δn = 0.001. FDTD simulations correlate Δφ and reflectance (ΔR) shifts with Δn_local. By analyzing resonant angle and intensity shifts, we determine the Δn_local. Temperature changes, altering the IL density, shift the refractive index, where a 10°C increase causes a 0.2° resonance shift, corresponding to a 0.005 refractive index reduction. This technique can differentiate ionic dynamics at interfaces from bulk solution responses.