Investigation on hydrogenation performance of Mg2Ni+10 wt.% NbN composite

•NbN is introduced into Mg2Ni hydride by Ar protected ball-milling.•Surfaces of the additive NbN particle are reduced by Mg2NiH4.•Hydrogenation kinetic property at 423 K is double improved.•Dehydrogenation capacity at 523 K of composites is beyond double improved.

The Mg2Ni+10 wt.% NbN composite was prepared by mechanical milling and its hydrogen absorption/desorption properties and microstructure were systematically investigated. XRD results indicated that NbN was stable during ball milling process while partly decomposed into NbN0.95 and NbH during hydriding/dehydriding cycles irreversibly. The composite exhibited excellent hydrogenation/dehydrogenation kinetics performance with 2.71  wt.% hydrogen absorbed in 60 s at 423 K and 0.81  wt.% hydrogen released in 2 h at 523 K, respectively. The H diffusion constant of the composite reached 14.98×10−5 s−1 which was more than twice increased than that of pure Mg2Ni powder. The superior hydrogen storage properties of the composite were ascribed to the refined grain size and abundant N-defect points provided by NbN and NbN0.95 in the composite.

Graphical abstractThe Mg2Ni+10 wt.% NbN composite displays improvements on particle size distribution as well as hydrogen storage properties compared with that of pure Mg2Ni.Figure optionsDownload full-size imageDownload as PowerPoint slide