Quantitative analysis of polarization kinetic for proton electrolyte membrane electrolyzer using the distribution of relaxation times of impedance

Investigating and interpreting the polarization kinetic processes occurring on different time scales within proton exchange membrane (PEM) electrolyzers is crucial for managing hydrogen production systems. The electrochemical impedance spectrum (EIS) is a popular technique for analyzing polarization kinetic from a frequency-domain perspective. In this work, the distribution of relaxation times (DRT) is applied with its strong discriminatory power to provide a refined kinetic analysis of the EIS. First, impedance spectrum measurements are performed under a wide range of operating conditions, including different current densities, flow rates, and temperatures. By analyzing variation trends in relaxation time peaks, five kinetic processes related to proton transfer, hydrogen evolution, oxygen evolution, and gas transport within the catalyst and porous transport layers are effectively delineated. Then, the losses for each polarization kinetic process are quantitatively extracted by integrating the relaxation times. Based on this, for the first time, the sensitivity of each kinetic loss to various operating conditions under different load states is analyzed by multiple stepwise regression analysis. It is found that the current density and operating temperature have a significant impact on each kinetic loss, while the flow rate only has a noticeable effect when the mass transfer loss is substantial. These efforts represent a comprehensive and systematic guideline for PEM electrolyzers using the distribution of relaxation times, which can also guide the selection of optimal operating conditions for PEM electrolyzer system management.