Interactions between Hydrogen and Palladium Nanoparticles: Resolving Adsorption and Absorption Contributions

Despite the apparent simplicity of palladium hydride systems, interactions between hydrogen and palladium are multifaceted. Electrochemical hydrogen stripping allows measuring the stoichiometric coefficient of hydrogen atoms inside PdH_x structures, whose properties greatly depend on x. In this paper, the insertion of H into Pd nanoparticles has been studied in a three-electrode setup (RDE) and a proton pump cell. An original way of modelling the hydrogen desorption curve is proposed, helping in the separation of hydrogen absorption from other contributions. The loading voltage exhibits the highest impact on the H absorption into Pd, reaching H_abs/Pd up to 0.47±0.02 in the RDE setup, at −0.2 V_RHE. Conversely, the loading duration presents only little influence in the very first seconds. Finally, maximal H_abs/Pd ratios are measured around 30–40 °C, likely due to an optimal balance between the H adsorption rate, and the H diffusion rate into Pd.