The significance of a polarization curve - analysis of a 60-cell polymer electrolyte water electrolysis stack

Abstract

The objective of this study is to demonstrate the diversity of information encapsulated within a polarization curve and its operational boundary conditions. To this end, a polymer electrolyte membrane water electrolysis stack comprising 60 cells with an active cell area of 1024 cm 2 has been constructed and characterized. The performance data such as the average cell voltage of 1.88 V ( η L H V = 66.6 % ) at the maximum applied current density of 3 A cm − 2 and a minimum specific power requirement of 4.01 kWh m N , H 2 − 3 at standard conditions at partial load ( 0.6 A cm − 2 , η L H V = 77.5 % ) were extracted from the polarization curve. In addition, the current-dependent single cell voltage distributions, the pressure and temperature differences for the anode and cathode sides could be determined, as well as the Faraday and voltage efficiency. The maximum Faraday efficiency recorded, was 97.6 % . A significant finding was the measurement of an H 2 in O 2 concentration of 0.11 % vol at 0.6 A cm − 2 which is far below the critical concentration of 4 % vol . Stack parameters and the begin-of-life state are determined based on the polarization curve and the supporting sensors.