In this work, we monitored Fe dissolu�on of a high electrochemical u�liza�on Fe-N-C catalyst using operando flow cell and GDE ICP-MS. We found that the fate of Fe-N-C catalysts is determined by combined Fe demetalla�on, reac�ve oxygen species ac�on (magnifying Fe demetalla�on) and local pH changes caused by ORR. We used a suite of complimentary preand post-mortem characteriza�on techniques (SEM, TEM, STEM, EDXS, EELS, Raman spectroscopy, XRD, XPS, XANES) to illustrate changes in structure and chemistry; based on our experimental insights, we built a microkine�c modelling to interpret our observa�ons.