The behaviors of the electrosorption of hydrogen into untreated and annealed Pd thin foil were systematically investigated with a primary effort concentrated on the elucidating the effect of annealing on the hydrogen uptake capacity. The change of the crystalline structure of Pd during the annealing process was monitored by in situ X-ray diffraction. The scanning electron microscopic images revealed the significant effect of the annealing temperature on the morphology of the Pd thin foil. Cyclic voltammetric and chronoamperometric techniques were employed to study the kinetics of hydrogen electrosorption, where alpha phase, beta phase and their transition were determined with respect to the electrode potential. The morphological and structural changes, as well as lattice parameters, played an important role in the hydrogen uptake. The Pd thin foil annealed at 700 degrees C exhibited an over 19-fold increase in hydrogen uptake capacity in comparison to the untreated one. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.