Spatially resolved model of oxygen reduction reaction in silver-based porous gas-diffusion electrodes based on operando measurements

Abstract

An improved spatially resolved mathematical model for porous, silver-based gas-diffusion electrodes for the oxygen reduction reaction in strongly alkaline electrolyte is presented. For the first time, important parameters describing the distribution of the liquid electrolyte in the electrode were determined via independent operando synchrotron experiments. With the model, a reasonable description of the overvoltage as a function of the current density at 80 °C could be achieved in a range of electrolyte concentrations (27 – 36.6 wt.% NaOH) and oxygen contents (20 – 100 vol.%). Model-based analysis of the processes inside the electrode revealed that a complex water cycle evolves which supports the removal of hydroxide ions and thus boosts the electrode performance. The analysis also showed that additional operando measurement of the electrolyte distribution and investigations with electrodes having a defined thickness of the reaction layer will help to further improve the model.