Bifunctional silver gas diffusion electrodes for metal-air batteries

Abstract

Gas diffusion electrodes with silver catalysts show a high activity towards oxygen reduction reaction in alkaline media. For the use in future metal-air batteries with an aqueous alkaline electrolyte the activity in oxygen evolution is also very important and therefor has to be further investigated. Due to the poor stability of carbon materials at high potentials these gas diffusion electrodes were prepared without carbon to improve especially long-term stability. Gas diffusion electrodes were electrochemically investigated in a half cell. In addition to cyclic voltammograms electrochemical impedance spectroscopy (EIS) was carried out to identify loss mechanisms for ORR and OER. For the simulation of the impedance spectras two different models were used so consider the different behavior of the electrodes in ORR and OER. Investigations showed that silver electrodes exhibit reasonable current densities for both reactions and a very good long-term stability.