Hydrogen Trapping in Palladium Nanoparticles Revealed by Electrochemical, X‑ray Scattering, and Spectrometric Measurements

Palladium hydrides (PdH x ) present a model system of both fundamental and applied importance: solute-induced phase transition affects evolution and electrooxidation of molecular hydrogen in water electrolyzers and fuel cells, respectively, as well as hydrogen storage, its sensing and catalysis of many hydrogenation reactions. It is well documented that hydrogen (H) atoms get progressively trapped in Pd under various sorption–desorption modes, leading to embrittlement and influencing its bulk and interfacial properties. However, the intensity and progressiveness of this phenomenon remain little explored. Herein, by combining in situ X-ray scattering and electrochemistry, we provide evidence of continuous expansion of the lattice of 3.6 nm carbon-supported Pd nanoparticles during repeated H insertion/de-insertion cycles, resulting in a progressive loss of their reversible H sorption capacity.