Atomic-scale details of hydrogen reactions mechanisms

In the frame of the HERMES H2020 project, we aim at determining the thermodynamics and the kinetics of H adsorption, H absorption and H desorption processes (potential of insertion/de-insertion, value of x) onto Pd nanocrystallites (NC). The H loading was determined from electrochemical experiments performed at LEPMI and correlated in situ to lattice parameter expansion using wide-angle X-ray scattering measurements (in house beamtime at ID31). However, open questions remain regarding the mechanism and the kinetics of hydride nucleation (preferential sites for nucleation or homogeneous nucleation at the whole particle surface) and growth (sharp for alphat to beta phase transition or coexistence of two-phases).