Spring Effect Endowing P-doped Li3VO4 With Long-standing Catalytic Activity for Tuning Cycling Stability of MgH2

Magnesium hydride (MgH 2 ) is a promising hydrogen storage material for its high hydrogen capacity of 7.6 wt.%. However, the further application is severely hampered by the sluggish reaction kinetics and stable thermodynamics. Introducing catalysts is an effective method to improve the reaction rate, but the catalytic activity tends to decrease with an increasing number of reaction cycles, due to the highly reductive Mg and H species. Herein, the spring effect has been observed in the P doped Li 3 VO 4 , in which both V─P and V─V bonds undergo compression and elongation during hydrogen absorption and desorption, respectively. Such a unique self-regulation spring effect not only improves the reaction kinetics of MgH 2 , but also maintains the high activity of P doped Li 3 VO 4 , thereby ensuring the hydrogen capacity of MgH 2 even after 100 loops. This spring effect of chemical bonding, stretched-recovered-stretched with the motion between the highly reductive Mg and H species, will provide insight into catalyst design for hydrogen-related industries.