Platinum group metal (PGM) nanocrystals (NCs) and their alloys are frequently used as catalysts in many relevant (electro)-chemical processes. In this proposal, we intend to follow the formation and propagation of structural defects as well as strain changes of multiple single Pt NCs under realistic electrochemical reactions (e.g. oxygen reduction reaction – ORR), these two parameters being descriptors of the ORR kinetics. This approach will complement the study of single-crystal samples performed by coherent Bragg diffraction by providing a more statistical approach.