Analysis of Electrochemical Impedance Spectroscopy Using Distribution of Relaxation Times for Proton Exchange Membrane Fuel Cells and Electrolyzers

Abstract

The research and development of proton exchange membrane fuel cells (PEMFCs) and proton exchange membrane water electrolyzers (PEMWEs) is essential for the implementation of the hydrogen economy [1]. Electrochemical impedance spectroscopy (EIS) gives insight to the electrochemical behavior of these energy conversion devices. The analysis of EIS for PEMFCs and PEMWEs has typically been performed using electrochemical equivalent circuits (EEC), which has identified significant kinetic, ohmic, and concentration electrochemical processes affecting cell performance [2,3]. EEC has the disadvantages of multiple circuit configurations fitting EIS data and requiring extensive background knowledge on circuits and electrochemical behavior. This results in multiple explanations for the electrochemical behavior of a cell, as well as the need for experience in building and understanding circuit configurations.This work explores the application of distribution of relaxation times (DRT) as an alternative EIS analysis tool to EEC for PEMFCs and, for the first time, PEMWEs. DRT and EEC were used to analyze the EIS data over a range of current densities for one PEMFC and two PEMWEs. Comparison between the two analysis tools shows that DRT can provide superior insight to the electrochemical behavior of these cells compared to EEC. DRT analysis identified the electrochemical processes revealed by EEC, as well as additional distinct electrochemical resistances [4,5]. DRT was shown to be applicable for PEMWE EIS analysis. Additional tests have been conducted in order to understand the origin of the additional processes identified by DRT for both PEMFCs and PEMWEs, and the results are discussed in detail in this work.