In-situ investigation on hydrogenation-dehydrogenation of Pd–Ag alloy films

Abstract

The present work reports on synthesis of Pd–Ag nano-composite films by magnetron co-sputtering and the structural changes in the alloy film during hydrogenation and dehydrogenation. Synchrotron X-ray diffraction is employed in-situ to reveal subtle structural changes occurring during hydrogenation and dehydrogenation processes, an aspect not investigated so far. It is revealed that the nanocomposite film having 88 at% Pd shows the formation of α-phase as an intermediate phase, however, completion of the hydrogenation process yields only β-phase. No β-phase formation is observed in nanocomposite thin film containing 54 at% of Pd, suggesting the suppression of formation of β-phase with increase in Ag concentration. On dehydrogenation, the peak returns to its original position i.e. the value before hydrogenation. The data also demonstrated that the addition of Ag in Pd results in complete removal of dissolved hydrogen thereby eliminates the problem of hysteresis. The study shows that the lower concentrations of Ag in Pd are better in terms of extent of peak-shift on hydrogenation/dehydrogenation and faster response/recovery kinetics.