Surface Structures and Hydrogenation Properties of Ti–Pd Alloys Immersed in Hydrogen Peroxide

抄録

This study achieves an increase in Pd concentration on the surface of Ti–Pd alloys using hydrogen peroxide as a green dealloying method, as well as determining the effect of Pd on the hydrogenation of the Ti–Pd alloys. Spontaneous oxidation of Ti in Ti–Pd alloys has been reported to precipitate low-valent Pd on the surface, which can be used for fast δ-TiH₂ formation and as a catalyst for various organic reactions. On the other hand, spontaneous oxidation has limited potential to increase the surface Pd concentration. As most of the Pd remains in the metallic phase, there is a need to increase the utilization of the remaining Pd. H₂O₂ is known to be a green oxidant and also forms complexes with Ti, therefore surface Pd enrichment by dealloying is expected. This study was carried out to investigate the relationship between hydrogenation and surface properties of Ti–Pd alloys by H₂O₂ immersion. The increase in the thickness of Ti oxide layers and the increase in Pd concentration on Ti–Pd alloys were found by H₂O₂ immersion. Model experiments on chip-like specimens showed that the Ti oxide layer retards hydrogen diffusion, while the Pd on the surface has the effect of increasing the hydrogen supply to the metallic phase. Pd on the surface was also found to have an effect on the fast decomposition of H₂O₂. These results indicate that H₂O₂ immersion is effective as a surface treatment to increase the Pd concentration on the surface with reduced Ti dissolution.