Hydrogen storage properties of spark generated palladium nanoparticles

Palladium nanoparticles of ∼4 nm were synthesized using spark discharge generation, and their hydrogen storage properties were determined using both thermal desorption spectroscopy (TDS) and Sievert’s (PCT) measurements. PCT measurements indicate that the thermodynamic properties of the nanoparticles towards hydrogen storage differ significantly from that of bulk Pd, even after sintering of the crystallites to 24 nm as determined using X-ray diffraction (XRD). Both the enthalpy and entropy of hydrogen absorption and desorption differ from bulk values, resulting in less hysteresis between absorption and desorption equilibrium plateau pressures and a lowering of the critical temperature of hydride formation Tc by approximately 100 K. The TDS measurements indicate a transition from diffusion to surface-barrier limited hydrogen desorption when going from Pd foil to Pd nanoparticles. This results in a strong decrease in the hydrogen thermal desorption temperatures by ∼160 K during TDS. These results indicate that spark discharge is an interesting method for metal hydride nanoparticle generation.