Kinetics of Hydrogen Absorption in Individual α-Phase Palladium Nanoparticles

Palladium hydrogen is a useful model in the study of both hydrogen absorption for energy storage, and lattice gas systems for fundamental thermodynamic models. Using in situ time-resolved X-ray nanodiffraction at the fourth generation Extremely Brilliant Source of the European Synchrotron (ESRF-EBS), the kinetics of hydrogen absorption in individual α phase Pd nanoparticles is examined. Hydrogen absorption kinetics in a gas reactor and an electrochemical cell are compared. Combining the individual nanoparticle X-ray measurements with chronoamperometry measurements, the kinetics of the ensemble of Pd nanoparticles on the glassy carbon substrate is compared with kinetics at the single nanoparticle level. Hydrogen absorption in α phase Pd in the electrochemical system is found to be slower than that of the gas system. Furthermore, the absorption in the electrochemical system slows down as the electrochemical potential is lowered. This slow down is found to be directly related to the increasing hydrogen absorption per step in electrode potential. Furthermore, differences between absorbed-quantity normalized absorption times is seen between the hydrogen and deuterium absorbates. Sieverts’s law of absorption is also shown to hold for individual Pd nanoparticles in the α phase.