Mapping of the Degradation Processes at Bifunctional O2 Gas Diffusion Electrode for Aqueous Alkaline Metal-Air Batteries

Rechargeable aqueous alkaline zinc-air batteries present, in principle, auspicious characteristics for the stationary storage of electricity produced by intermittent renewables. Still, a number of issues associated with the durability of the electrocatalytic performances of the air cathode hinder further implementation of this battery technology. A recent article (J. Power Sources 482 (2021) 22890) details a high-performance gas diffusion electrode (GDE) embedding a bi-functional catalyst for the oxygen evolution and oxygen reduction reactions. Now, aiming at a better understanding of the degradation processes taking place at such electrode, we detail a multi-scale approach based on a combination of results from electrochemical, electron imaging and spectroscopic techniques (EIS, SEM, XPS, operando EXAFS). Insights gained resolve the main degradation processes occurring at different length-scales (Å vs. μm), chemical and structural changes at the electrode components level, as well as of their interrelations. The resulting mapping realized at the gas diffusion electrode level and under current loads relevant for practical application paves the way for further improvements of the electrode architecture. In addition, model quantitative XPS analysis, cell design for operando EXAFS and differential analysis of the EXAFS data introduced herein, are applicable to any type of GDE architecture for electrode durability studies