Abstract: Rhodium-platinum core-shell nanoparticleson a carbonsupport (Rh@Pt/C NPs) are promising candidates as anode catalystsfor polymer electrolyte membrane fuel cells. However, their electrochemicalstability needs to be further explored for successful applicationin commercial fuel cells. Here we employ identical location scanningtransmission electron microscopy to track the morphological and compositionalchanges of Rh@Pt/C NPs during potential cycling (10 000 cycles,0.06-0.8 V-RHE, 0.5 H2SO4)down to the atomic level, which are then used for understanding thecurrent evolution occurring during the potential cycles. Our resultsreveal a high stability of the Rh@Pt/C system and point toward particledetachment from the carbon support as the main degradation mechanism.