Figure 1. Schematization of the electrochemical double layer probing by APXPS under polarization conditions.

(a) EDL probing using a gold polycrystalline working electrode (WE) in KOH 0.4 mM aqueous solution (d_EDL=15.2 nm) containing 1.0 M pyrazine (SLI, solid/liquid interface, LGI, liquid/gas interface, and Py ESF, pyrazine at the electrode surface). (b,c) Schematic representing the spectral broadening of the core level of the elements belonging to the liquid phase, passing from the potential of zero charge (PZC) to a positive potential applied to the WE, respectively. The function S represents the detected liquid phase related-core level, which is given by the convolution of the binding energy (BE)-shifted spectra of the molecules in solution (s_j[BE(z_j)]) as a function of their position within the potential drop with respect to the WE surface (z_j).