Numerical analysis of the electrochemical dissolution of iridium catalyst and evaluation of its effect on the performance of polymer electrolyte membrane water electrolyzers

Abstract

A physicochemical model of a water electrolyzer with a polymer electrolyte membrane (PEM) was developed, taking into account the electrochemical dissolution of an anodic iridium catalyst. The dependencies of the rates of iridium loss and electrolysis voltage increase upon the current density were calculated in order to analyze the effect of the iridium dissolution on degradation of the electrolysis cell (EC) performance. As an estimated characteristic of the techno-economic costs of the electrolysis process, the amount of iridium loss from the anode catalyst layer (as a result of electrochemical dissolution) in the course of the generation of 1 kg of hydrogen was calculated. Data were analyzed and a number of regularities of the iridium dissolution and its influence on the rate of degradation of the EC performance were found. In particular, the most efficient ECs in terms of electrolysis voltage (energy consumption for gas production) are, simultaneously, the most unstable (prone to performance degradation) in relation to the iridium dissolution process. An aim of current requirements for water electrolyzers includes reducing the specific consumption of iridium required for hydrogen generation.