Experimental and Model-Based Analysis of Electrolyte Intrusion Depth in Silver-Based Gas Diffusion Electrodes

Abstract

The electrolyte distribution is a central point of discussion for understanding the processes inside gas-diffusion electrodes (GDE) for the oxygen reduction reaction in highly alkaline media. During first radiographic operando synchrotron experiments, the liquid electrolyte was located, however, the through-plane distribution remains unclear. Therefore, model electrodes consisting of nickel and silver layers are developed to determine the electrolyte intrusion depth. Nickel-based GDEs are modified to achieve a pore system morphology suitable for the oxygen reduction reaction and subsequently coated with silver-PTFE catalyst layers. These graded electrodes form gas-diffusion (nickel) and reaction (silver) layers. The electrodes performance is determined under industrial conditions (80 °C, 30 wt % NaOH electrolyte) as a function of the silver layer thickness and thus of the effective intrusion depth of the electrolyte. The model-based analysis confirms the experimental determined intrusion depths. Nevertheless, additional operando tomography measurements would help to further improve the understanding of the processes inside GDE.