Application of Distribution of Relaxation Times Method in Polymer Electrolyte Membrane Water Electrolyzer

Abstract

Distribution of relaxation times (DRT) is a well-established way of deconvoluting electrochemical impedance spectroscopy (EIS) data from electrochemical component, such as fuel cells and battery, which can provide a deeper insight into electrode reactions and give the different time constant in each process, besides, it can be used to develop the most accurate equivalent circuit models without the input of any information of circuit architecture. This paper first implemented DRT methods in the polymer electrolyte membrane water electrolyzer (PEMEC), besides, and the regularization parameter, characteristic parameters and frequency factors of solving process are introduced. The results show that (1) DRT method represents the original impedance spectrum of hydrogen production in the form of three characteristic peaks, which correspond to the main polarization processes in hydrogen production system, including water/gas diffusion, hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) reactions and proton transfer processes, respectively, besides, the number of peaks is the number of each RQ loop. (2) The optimal regularization parameter is 0.01 in different current and temperature. (3) The frequency of water/gas diffusion, HER and OER reactions and proton transfer processes is 0.1-60Hz, 100-1000Hz and 2000-4000Hz, respectively. (4) DRT methods couples with genetic algorithm can effectively identify various types of polarization impedance corresponding to different characteristic frequencies without equivalent circuit model.

Keywords: PEMEC, DRT, HER and OER reactions, Proton transfer, Genetic algorithm