Effect of rGO supported NiCu derived from layered double hydroxide on hydrogen sorption kinetics of MgH₂

A reduced graphene oxide-supported NiCu nanocatalyst (NiCu/rGO) was prepared via the reduction of self-assembled layered double hydroxide (LDH) and graphene oxide (GO) composite precursor. The effect of NiCu/rGO on the hydrogen sorption kinetics of MgH₂ was investigated systematically. TEM observations reveal that the ultrafine NiCu (6 nm) particles highly disperse on the rGO surface. Hydrogen storage measurements reveal that MgH₂-5 wt.% NiCu/rGO has superior hydrogen sorption kinetics over as-milled MgH₂ and MgH₂-5 wt.% NiCu without rGO. MgH₂-5 wt.% NiCu/rGO absorbs 5.0 wt% hydrogen within 100 s at 200 °C, while MgH₂-5 wt.% NiCu only absorbs 2.0 wt% hydrogen and as-milled MgH₂ hardly absorbs hydrogen under the same conditions. Moreover, MgH₂-5 wt.% NiCu/rGO starts to desorb hydrogen at 185 °C, which is 115 °C lower than that of as-milled MgH₂, and desorbs 5.8 wt% hydrogen within 1200 s at 300 °C. The apparent activation energy for hydrogen desorption of MgH₂-5 wt.% NiCu/rGO is 71.7 kJ/mol H₂, significantly lower than 107.3 kJ/mol H₂ for MgH₂-5 wt.% NiCu. The enhanced hydrogen sorption kinetics of MgH₂-5 wt.% NiCu/rGO mainly attributes to the synergistic effect between rGO and NiCu nanoparticles. This research extends the knowledge of designing efficient catalyst via layered double hydroxides precursor in the hydrogen storage materials.