For lab-scale electrocatalysis studies, one typically uses a three-electrode system, which consists of working, counter (auxiliary), and reference electrodes, an electrolyte solution, and a reactor. In this system, it is important for accurate electrochemical studies to select an appropriate reference electrode for a particular electrolyte solution and recognize the presence/absence of liquid junction potential at the frit of a reference electrode. For instance, in alkaline water electrocatalysis experiments, Hg/HgO, Ag/AgCl, or saturated calomel electrode (SCE) is generally used as a reference electrode, and 1 M KOH/NaOH aqueous solution is utilized as an electrolyte solution.1 In this regard, the Ag/AgCl electrode and SCE are unsuitable for electrochemical studies with alkaline electrolytes, and among them, only the Hg/HgO electrode can be used instead.1 Furthermore, if the internal solution of a reference electrode and the external electrolyte solution are different in constituent and/or concentration, the liquid junction potential will be established at the frit of a reference electrode. In this case, to accurately know the potential applied to a working electrode, this liquid junction potential as well as the iR drop caused by solution resistance need to be considered and corrected appropriately. However, the liquid junction potential has so far been ignored in most of the electrocatalysis studies.In this work, we will discuss a method to experimentally estimate the liquid junction potential at the reference electrode frit using three-electrode systems with different combinations of electrolytes and reference electrodes. Herein, we will deal with alkaline water electrolysis systems as representatives. The as-estimated values of various liquid junction potentials will be compared with the theoretical values obtained using the Henderson equation2 and the stationary Nernst–Planck equation.3 Additionally, the guideline for selecting an appropriate reference electrode depending on the types of external electrolyte solutions will be discussed briefly. We believe that these findings can improve the accuracy of reporting potential-related parameters (e.g., overpotential, half-wave potential, onset potential, etc.) in three-electrode system-based electrocatalysis studies. References K. Kawashima et al., ACS Catal., 13, 1893–1898 (2023).R. G. Bates, Determination of pH, 2nd ed., p. 36–44, A Wiley-Interscience Publication, New York, New York, (1973).M. Marino, L. Misuri, and D. Brogioli, (2014) https://arxiv.org/abs/1403.3640v2.