In this proposal, we intend to follow and study the structural changes in three dimensions (3D) of multiple Pt nanoparticles (NPs) under realistic electrochemical reactions, such as oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER). More precisely, we aim to map the strain response of multiple single NPs as a function of the electrode potential by probing the particles at different Bragg peaks to get the full 3D strain tensor. The Pt NPs will be immersed in H2SO4 and the electrode potential will be applied to trigger different reactions (e.g ORR, HER). This experiment will complement previous studies carried out at ID01 beamline.