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

Abstract

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.