Degradation Mechanisms of Oxygen Evolution Reaction Electrocatalysts: A Combined Identical-Location Transmission Electron Microscopy and X-Ray Photoelectron Spectroscopy Study
Résumé
Determining the degradation mechanism of oxygen evolution reaction (OER) catalysts is fundamental to design improved polymer electrolyte membrane water electrolyser (PEMWE) devices. In this study, we combined identical-location transmission electron microscopy, X-ray photoelectron spectroscopy and inductively coupled plasma mass spectrometry to determine the changes in morphology and composition of iridium nanocatalysts covered by a thin oxide layer (IrO x) in simulated PEMWE anode operating conditions. The results show that iridium valency increased rapidly during a conditioning step and in a softer manner after electrolysis. The catalysts containing initially metallic iridium were composed of a mix of Ir(III), Ir(IV) and Ir(V) after OER conditions while catalysts containing initially Ir(IV) solely had the same composition after OER. IL-TEM images show that Ir dissolution/redeposition and particle detachment occurred during electrochemical conditioning while agglomeration/coalescence and dissolution were observed after electrolysis. Iridium dissolution was quantified after a constant current electrolysis and we observed a direct relationship between the proportion of Ir(IV) in the catalysts and their stability in OER conditions. Figure 1: ILTEM images of IrO x nanoparticles supported on antimony-doped tin dioxide aerogel before/after 50 k potential cycles between 1.2 < E < 1.6 V vs. RHE.
Domaines
Catalyse
Origine : Fichiers produits par l'(les) auteur(s)