The Effect of Water Treatment Processes on the Performance of Proton Exchange Membrane Water Electrolysis

This study investigates performance variation and cell degradation in proton exchange membrane water electrolysis (PEMWE) systems depending on feed water quality. In commercial PEMWE designs, simplified water treatment configurations focusing primarily on electrical conductivity (EC) control are sometimes adopted instead of conventional full ultrapure water production processes. To evaluate the impact of different water treatment processes on cell degradation, permeates from various processes were used as feed water, and cell voltage patterns were analyzed based on EC and total organic carbon (TOC) levels. The experimental results demonstrated that both the two-pass reverse osmosis (RO) and mixed-bed polisher (MBP) permeates achieved an EC below 1 μS/cm, meeting the minimum required standard. Although the cell voltage increase trends for both permeates were similar, the MBP permeate exhibited a higher TOC level despite its lower EC. The elevated TOC level observed in the MBP permeate is attributed to the low organic matter rejection rate of the RO membrane used in the preceding process. This highlights that in simplified water treatment processes for PEMWE, implementing a two-pass RO configuration is essential for effective TOC control. However, simply introducing this configuration is insufficient; it must be accompanied by strategic RO membrane selection to ensure stable operation of PEMWE systems.