NiPd Nanoparticles\nDeposited on CeO<sub>2</sub> Nanorods\nas Catalysts for Enhancing Hydrogen Storage in MgH<sub>2</sub>

Magnesium hydride (MgH<sub>2</sub>) stands out as one\nof the most\npromising hydrogen storage materials due to its high hydrogen storage\ncapacity and low cost. Nevertheless, its sluggish kinetics and remarkable\nstability pose significant challenges, restricting its widespread\npractical application. In this study, we successfully synthesized\na CeO<sub>2</sub>-supported NiPd catalyst (NiPd/CeO<sub>2</sub>) by\nfirmly embedding a small amount of Ni<sub>0.5</sub>Pd<sub>0.5</sub> alloy nanoparticles on CeO<sub>2</sub> nanorods. This catalyst notably\nlowered the initial dehydrogenation temperature of MgH<sub>2</sub> from over 300 to 219 °C. When 10 wt % of the NiPd/CeO<sub>2</sub> was incorporated into MgH<sub>2</sub>, the resulting composites\nexhibited impressive hydrogen storage kinetics. Specifically, they\nwere able to release approximately 6 wt % H<sub>2</sub> within 500\ns at 350 °C and absorb about 6.4 wt % H<sub>2</sub> in just 40\ns at 250 °C. Furthermore, these composites showed excellent cycling\nstability, maintaining over 90% of their hydrogen storage capacity\nafter 20 cycles. Combining multiple characterization techniques revealed\nthat the excellent catalytic performance was primarily attributed\nto the rich oxygen vacancies on the CeO<sub>2</sub> nanorods, which\nfacilitated the strong embedding of Ni<sub>0.5</sub>Pd<sub>0.5</sub> nanoparticles on CeO<sub>2</sub>. This, in turn, led to a synergistic\neffect between Ni, Pd, and CeO<sub>2</sub>. The <i>in situ</i>-formed Mg<sub>6</sub>Ni/Mg<sub>6</sub>Pd functions as a “hydrogen\npump”, facilitating enhanced hydrogen absorption and dehydrogenation\nprocesses in MgH<sub>2</sub>. These results offer valuable insights\ninto the design of catalysts and the identification of active species\ninvolved in modifying MgH<sub>2</sub>.