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The development of high-efficiency carbon-based multifunctional catalysts is of great significance for improving solid-state hydrogen storage materials. Herein, it was confirmed that CoMoO 4 sheet-like nanocatalysts uniformly supported on the surface of reduced graphene oxide (CoMoO 4 /rGO) were successfully prepared by a simple hydrothermal reaction. The novel CoMoO 4 /rGO catalyst was subsequently doped into MgH 2 to improve its hydrogen storage performance. MgH 2 –10 wt% CoMoO 4 /rGO starts to release hydrogen at around 204 °C, which is about 36 °C and 156 °C lower than that of MgH 2 −10 wt%CoMoO 4 and pure MgH 2 , respectively. In addition, 6.25 wt% H 2 can be released within 10 min at 300 °C. After complete dehydrogenation, H 2 can be absorbed below 80 °C. Meanwhile, it can absorb 4.2 wt% H 2 in 20 min under the condition of 150 °C and 3 MPa. Moreover, the activation energy of hydrogen absorption and dehydrogenation of MgH 2 –10 wt%CoMoO 4 /rGO composites are reduced by 31.44 kJ mol−1 and 33.78 kJ mol−1, respectively, compared with pure MgH 2. Cycling experiment shows that the MgH 2 –10 wt%CoMoO 4 /rGO composite system can still maintain about 98% of the hydrogen storage capacity after 10 cycles. Furthermore, studies on the catalytic mechanism show that the synergistic effect between the in-situ generated MgO, Co 7 Mo 6 and Mo may help to promote the diffusion of H 2 , thereby improving the MgH 2 Hydrogen storage properties. • MgH 2 –10 wt%CoMoO 4 /rGO composite system was reported for the first time. • MgH 2 –10 wt%CoMoO 4 /rGO composite material starts dehydrogenation at about 204 °C. • MgH 2 –CoMoO 4 /rGO composites showed promising kinetic properties. • MgH 2 –CoMoO 4 /rGO composites showed good cyclic stability. • MgO, Mo and Co 7 Mo 6 were formed in situ during the reaction. [ABSTRACT FROM AUTHOR]

• Nano NiO/C catalysts were prepared by ultrasonic oscillation and calcination. • Hydrogen could be released at 195 °C and absorbed at 50 °C for the composite. • De/hydrogenation activation energy of the composite were significantly reduced. • The composite material had good cyclic reversibility. • Ab initio calculations showed that NiO and Mg 2 Ni could improve the diffusivity of H atoms. Magnesium based solid hydrogen storage material (MgH 2) has the advantages of good safety and high hydrogen storage capacity in the shipping field. However, the high hydrogen absorption and desorption temperature have not been well solved. Herein, this work proves that it is very effective to improve the hydrogen storage performance of MgH 2 by doping nano NiO/C catalyst. Specifically, experimental results showed that MgH 2 + 9 wt% NiO/C composite could dehydrogenate at 195 °C, which was 155 °C lower than pure MgH 2. In addition, 6.21 wt% H 2 could be released rapidly at 300 °C for 10 min. After complete dehydrogenation, the absorption rate of hydrogen is 50 °C, which is 80 °C lower than that of pure MgH 2. Moreover, 5.13 wt% H 2 could be absorbed within 1 h at 125 °C and 3 MPa hydrogen pressure. In addition, dehydrogenation and hydrogen absorption apparent activation energies of MgH 2 + 9 wt% NiO/C composite are 70.26 kJ/mol and 25.55 kJ/mol lower than those of pure MgH 2 , respectively. The cycle experiment showed that MgH 2 + 9 wt% NiO/C had excellent cycle stability and could maintain 98.8% hydrogen storage capacity after 20 cycles. Furthermore, the study of the catalytic mechanism indicated that NiO/C catalyst is evenly distributed on the surface of MgH 2. More importantly, Mg 2 Ni/Mg 2 NiH 4 is generated in situ, which acts as a "hydrogen pump" and speeds up hydrogen diffusion during the hydrogen absorption and desorption cycle. [ABSTRACT FROM AUTHOR]