The electrochemical potential of an interface can be controlled by a potentiostat, which regulates the potential difference between the working and the reference electrodes. Under transient conditions, the electrochemical potential may deviate from the applied potential due to the Ohmic resistance (the RC element in the circuit). However, characterizing this deviation has been challenging. In this thesis, an optical method based on second harmonic generation (SHG) spectroscopy is used to monitor the electrochemical potential at the platinum (Pt)–water interface during a potential sweep. The results are compared to the constant potential baseline. We observe the deviation between the electrochemical potential and the applied value and that this gap widens with the potential sweep rate. This observation is consistent with the Ohmic resistance limitation; however, even after correcting for the Ohmic drop, the gap between the electrochemical potential and the applied value persisted, especially at high scan rates. This finding suggests that there is an intrinsic reorganization of the electrical double layer (EDL) beyond the Ohmic contribution. Our finding highlights the EDL dynamics beyond the equivalent circuit model and that the interpretation of the transient potential analysis may not as straightforward as previously considered.