Impedance Measurements of Silver Gas Diffusion Electrodes during Oxygen Reduction in Alkaline Solution

Kurzfassung

In order to analyze in detail the kinetics of the oxygen reduction reaction (ORR) in alkaline solution (25 wt% KOH and 10 N NaOH) of PTFE-bonded Gas Diffusion silver Electrodes (GDEs) electrochemical impedance measurements, current-voltage curves and XPS measurements have been performed. GDE with dispersed silver catalyst were produced by electrochemical reduction of silver oxide-GDE. The silver GDEs were produced by the Reactive Mixing and Rolling (RMR) production process and multilayer electrodes by combination of RMR with dry spraying of a silver catalyst layer on inert graphite GDE. The electrochemical impedance spectra (EIS) were recorded in the frequency range 1 mHz to 64 kHz and 1 mHz to 100 kHz respectively. Silver is a known electrocatalyst for the reduction of oxygen in alkaline fuel cell cathodes. To enhance its catalytic activity, silver is used in high surface area forms such as porous electrodes where the silver particles are dispersed in the porous matrix.