Lars-Erik Owe

Materials for Electrocatalysis of Oxygen Evolution Process in PEM Water Electrolysis Cells

Proton exchange membrane (PEM) water electrolysis offers several advantages compared to the traditional alkaline technologies including higher energy efficiencies, considerably higher specific production rates leading to more compact design, and avoiding a liquid and corrosive electrolyte. The oxygen electrode is the critical part in the energy consumption of such cells. To obtain high performance, electrocatalytically very active anode materials have to be developed for oxygen evolution. The most promising electrocatalytic materials are based on IrO2 and RuO2, preferably in mixtures with other transition metal oxides with electronic conductivity. Excellent performance has been obtained by using nanocrystalline electrocatalysts based on iridium oxide with additions of ruthenium oxide and/or tin oxide, forming rutile structures, or mixed with tantalum pentoxide.This concept has been applied extensively in our work and has been successful in understanding oxygen evolution performance variations in IrO2-RuO2, IrO2-SnO2, IrO2-RuO2-SnO2 and IrO2-RuO2-Ta2O5 systems.

An Impedance Model for a Porous Intercalation Electrode with Mixed Conductivity

A mathematical model for the impedance of porous intercalation electrodes of mixed conductivity has been derived. The model is based on an agglomerate model and dilute-solution theory. With respect to the impedance of similar electrodes of metallic conductivity, two corrections were identified. The first is related to the diffusional component of interparticle transport in the porous electrode. The second is an impedance related to the exchange of electrons with the electrode at the electrode-support interface. These two corrections may lead to significant deviations in the low frequency region of the impedance spectra of the mixed conductor. In the high frequency region, however, no significant differences were found between the impedance of the metallic electrode and that of mixed conductivity for similar parameter sets. Recombination of charge carriers in the system has been included through a spherical Gerischer impedance, giving rise to substantial deviations in the low frequency regions if reaction rates are significant.