Exploring the hydrogen absorption into Pd–Ir nanoalloys supported on carbon

Comprehensive understanding of the hydrogen gas interaction with metal nanoparticles is crucial for the development of multifunctional materials. The hydrogen absorption properties of well-dispersed Pd–Ir nanoalloys on a mesoporous carbon are reported here. The average size of nanoalloys depends on the composition and is comprised between 2.7 and 3.5 nm with decreasing Ir content. Structural analysis evidences a single phase FCC structure for all nanoparticles and a linear variation of the lattice parameter with composition confirming the formation of nanoalloys in this bulk-immiscible system. The hydrogen absorption properties can be tuned by the chemical composition: Pd-rich nanoparticles form hydride phases, whereas Ir-rich phases do not absorb hydrogen under ambient temperature and pressure conditions. The thermodynamic properties of hydride formation in Pd-rich phases are altered relative to the bulk counterparts. Moreover, the hydrogen absorption capacity in Pd-rich nanoalloys is larger as compared to bulk alloys. This might be explained by an important finite size effect that increases the hydrogen absorption capability of Pd–Ir alloys at nanoscale.