Fig. 3. (A) Schematic depiction of the custom-designed, 3D-printed flow cell and electrochemical cell components. (B) Non-faradaic capacitance response, C of B15C5_SAM toward Na⁺ under continuous electrolyte flow (H₂O, 100 mM TEACl) in the custom flow cell (cell volume = 10 μL, flow rate Q = 100 μL min⁻¹, at fixed E = OCP and f = f_c). Each spike represents the response toward aliquots (V_sample = 1 mL) of Na⁺ of concentration increasing up to 50 mM. Subsequent washing of the interface with supporting electrolyte re-establishes the baseline (black lines) with excellent recovery (0.5 ± 0.3% h⁻¹).