Charge transfer between the MgH2 and TiO2 surface of the MgH2/TiO2/Ni3ZnC0.7 composite with good cyclic reliability

• Ni 3 ZnC 0.7 uniformly distributes on the surface of sheet MXene derived TiO 2 . • The MgH 2 -TiO 2 /Ni 3 ZnC 0.7 exhibits good cyclic reliability under 110 cycles. • TiO 2 regulates the coordination of H atoms, elucidating its role as a “charge regulator”. In order to improve the hydrogen storage properties of MgH 2 , the layered Ni 3 ZnC 0.7 loaded TiO 2 composite with bamboo-like carbon nanotubes on surface is prepared by filtration followed with calcination. The MgH 2 -2.5 wt% TiO 2 /Ni 3 ZnC 0.7 composite can absorb 4.13 wt% H 2 at 423 K and 600 s, and release 4.02 wt% H 2 at 573 K and 60 min. The hydrogen absorption/desorption activation energies are decreased to 41.92 and 95.18 kJ mol −1 H 2 , respectively. The hydrogen storage capacity exhibits little changes under different temperatures and pressures (110 cycles), clearly imply its cycle stability of this composite. The in-situ generated Mg 2 Ni/Mg 2 NiH 4 acts as a “hydrogen pump” providing additional channels for hydrogen diffusion and the presence of carbon nanotubes limits the aggregation and growth of Mg/MgH 2 particles. Moreover, multivalent Ti provides bridges and catalytically active sites for electron transfer between. During the broken process of Mg-H bonds, Bader charge maps indicate that H is bonded with Ti and Mg is bonded with O; After another MgH 2 absorbed, two H atoms are coordinated to Ti, implying that the TiO 2 acts as “charge regulator”. The deep understanding of the charge transfer between the MgH 2 and TiO 2 surface of the MgH 2 /TiO 2 /Ni 3 ZnC 0.7 composite should provide new sight for designing MXene and Ni 3 ZnC 0.7 derived catalysts.