CO2-Assisted Regeneration of a Polymer ElectrolyteWater Electrolyzer Contaminated with Metal Ion Impurities

Polymer electrolyte water electrolysis (PEWE) is perceived as a key technology for conversion of renewable electricity in large-scale energy storage applications and deep decarbonization of the traditionally carbon-intensive mobility and chemical industry sectors. Since the price of hydrogen produced by PEWE is dominated by the price of electricity, it is crucial to ensure low degradation rates during the lifetime of a PEWE stack. This study aims to shed light onto the effects of cationic impurities that are responsible for the water impurity related failures of a majority of commercial stacks by employing operando neutron imaging coupled with electrochemical impedance spectroscopy measurements. A detailed overpotential analysis is conducted to elucidate how different voltage losses are triggered depending on the relative position of the cationic contaminant in the catalyst coated membrane. Based on this, a novel, CO2 - assisted, method for the extraction of cationic impurities from the ionomer of the electrolyzer to recover performance during operation of the cell is presented. (C) The Author(s) 2019. Published by ECS.