Fast and real-time observation of hydrogen absorption kinetics for palladium nanoparticles

Structural change of Pd nanoparticles on aluminum oxide during hydrogen absorption reaction was directly observed by X-ray absorption fine structure with dispersive optics. Hydrogen pressure dependence of the expansion of the interatomic distance for Pd–Pd bonding in Pd nanoparticles was investigated by real-time-resolved and in situ observation with a rate of 50 Hz at room temperature. It has been revealed that the Pd nanoparticles show strong hydrogen pressure dependence of the reaction rate and the saturated interatomic distance for the hydrogen absorption. Determined reaction order implies that the rate of the hydrogen absorption reaction is limited by the surface dissociative adsorption step.

Research highlights▶ Hydrogen absorption kinetics for Pd nanoparticles was observed at 50 Hz. ▶ In situ and real-time-resolved XAFS observation detects the hydrogen absorption kinetics. ▶ Pd nanoparticles show complete expansion of interatomic distance in only 50 ms. ▶ Surface adsorption step of hydrogen is the limiting rate for absorption reaction.