“…Hydrogen trapping sites act as the center of segregation of hydrides even in hydrogen solid solution region [12]. Oxide/metal interfaces also tend to act as hydrogen trapping sites and form hydrides in the course of hydrogen absorption [13,14]. Based on these facts, we intentionally induced vacancies with high concentrations by ion irradiation in the surface region of Pd, and investigated the effect of the vacancy formation on the initial rate of hydrogen absorption of Pd in electrochemical process.…”