Ultrafast hydrogenation of magnesium enabled by tetragonal ZrO2 hierarchical nanoparticles

Transition metal catalysts are particularly effective in improving the reaction kinetics of light metal hydrides for reversible hydrogen storage . Herein, tetragonal ZrO 2 hierarchical nanoparticles (nano-ZrO 2 ) composed of primary particles of ∼4 nm in diameter are successfully synthesized by a facile one-pot solvothermal process. The unique hierarchical structure features homogeneous distributions of in situ formed multivalent Zr-based species, which allow superior catalytic activity for hydrogen storage in MgH 2 . The MgH 2 +10 wt% nano-ZrO 2 starts releasing H 2 at 163 °C after one activation, which is 107 °C lower than additive-free MgH 2 , and 50 °C lower than that of bulk ZrO 2 -doped MgH 2 . At 230 °C, 5.9 wt% of H is rapidly liberated within 20 min from the nano-ZrO 2 -containing MgH 2 . More importantly, the material shows superior hydrogenation kinetics compared with all reported catalyst-modified MgH 2 . The nano-ZrO 2 -containing Mg took up 4.0 wt% of H in only 12 s at 100 °C under 50 bar H 2 , 400 times faster than the bulk-ZrO 2 -modified sample. Even at 50 °C, approximately 1.8 wt% H was absorbed within 1 min. Our findings provide useful insights into the design and development of high-performance catalysts toward solid-state hydrogen storage materials.