The electrochemical hydrogen compressor (EHC) operates without the oxygen reduction reaction, inherently lacking water generation at the cathode. As a result, the polymer electrolyte membrane undergoes continuous dehydration via electroosmotic drag, leading to increased ohmic resistance and reduced system performance. This study investigates the relationship between membrane hydration and ionic conductivity using a custom‐designed conductivity cell with a Nafion 117 membrane. The results confirm a strong correlation between water content and proton conductivity. An empirical relationship is also derived to quantitatively estimate the ionic conductivity of the Nafion 117 membrane as a function of its hydration level. Furthermore, comprehensive analysis of hydrogen output, water vapor products, and impedance characteristics under various applied voltages reveals that operating the EHC at 1.70 and 1.95 V, where water electrolysis occurs, leads to decreases in hydrogen output by 4.2% and 15.7%, respectively, compared to operation at 1.45 V, where electrolysis is absent. Electrochemical impedance spectroscopy (EIS) further demonstrates increases in both ohmic and charge transfer resistances under electrolysis conditions. These findings underscore the importance of maintaining membrane hydration and avoiding water electrolysis to ensure optimal EHC performance. While the onset potential for water electrolysis was found to be 1.53 V in this system, this value is dependent on specific catalytic material and system configuration; thus, EHCs should be operated below the electrolysis threshold appropriate to their configuration. Overall, this study establishes a mechanistic understanding of how water transport and membrane hydration influence efficiency and degradation, advancing the scientific basis for next‐generation proton exchange membrane (PEM)‐based EHC design.
Kweon et al. (Thu,) studied this question.