PEM water electrolysis: steady-state, dynamic and degradation models of a cell, supported by EIS analysis

Abstract

PEM water electrolysis (PEMWE) cells are a promising solution for the production of hydrogen in the nearly future. These low temperature cells are able to work in a wide and variable range of current density, they are characterized by a fast response which make them the ideal candidate for being coupled with renewable energy systems, such as wind turbines and photovoltaics, whose electrical energy production is usually variable in time and unpredictable. In addition, degradation phenomena affect the cells during their operational life, leading to changes in their performance. From these peculiarities derives the need of models that can predict the behaviour of the PEMWE cells in the different conditions they are subjected to, taking into account also their losses in performance. Three different models have been developed for describing respectively the steady-state and dynamic conditions, and the degradation of the cell in time, which are easily coupled with the Electrochemical Impedance Spectroscopy (EIS) analysis results and the Electrochemical Equivalent Circuit (EEC) chosen. The steady-state polarization curve model has been experimentally validated, while no experimental tests have been done yet in order to validate the dynamic and the degradation models proposed.