Summary A traditional alkaline aqueous electrolyzer is investigated by using a 3‐electode structure that enables the reaction resistance of each individual electrode to be accurately monitored. Combining experimental observations with resistance‐based model analysis, we establish a quantitative relationship between current density and key voltage losses, including losses due to thermodynamics, kinetics, ohmic, and mass transport. These results demonstrate that the oxygen evolution reaction and bubble effects play crucial roles in determining electrolyzer performance. By varying the distance between electrodes, 2 effective OH− conductivities in 0.4M KOH are found to be 0.1333 and 0.9650 second cm−1, depending on bubble formation and release rate at the electrode interface. Moreover, bubble coverage on electrode surface achieves a steady state of 96% when current density is above 0.1 A cm−2. In the study of various electrolyte concentrations, all the model predictions show good agreement with experimental results, confirming its ability to capture actual cell performance. This newly presented empirical resistance‐based model provides a practical framework to simulate complicated electrolysis reactions, serving as a comprehensive guide for continuous improvement of water electrolysis.

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