Hydrogen storage properties of MgH2 co-catalyzed by LaH3 and NbH

Jian-Zheng Song,Rui-Dong Fu,Shu-Min Han,Xin Zhao,Zi-Yang Zhao

doi:10.1007/s12613-017-1509-z

Abstract

To improve the hydrogen storage properties of Mg-based alloys, a composite material of MgH2 + 10wt%LaH3 + 10wt%NbH was prepared by a mechanical milling method. The composite exhibited favorable hydrogen desorption properties, releasing 0.67wt% H2 within 20 min at 548 K, which was ascribed to the co-catalytic effect of LaH3 and NbH upon dehydriding of MgH2. By contrast, pure MgH2, an MgH2 + 20wt%LaH3 composite, and an MgH2 + 20wt%NbH composite only released 0.1wt%, 0.28wt%, and 0.57wt% H2, respectively, under the same conditions. Analyses by X-ray diffraction and scanning electron microscopy showed that the composite particle size was small. Energy-dispersive X-ray spectroscopic mapping demonstrated that La and Nb were distributed homogeneously in the matrix. Differential thermal analysis revealed that the dehydriding peak temperature of the MgH2 + 10wt%LaH3 + 10wt%NbH composite was 595.03 K, which was 94.26 K lower than that of pure MgH2. The introduction of LaH3 and NbH was beneficial to the hydrogen storage performance of MgH2.

Highlights

In recent years, new energy resources have been eagerly sought because fossil fuels are being gradually exhausted and their combustion products pollute our environment [1,2]
Phase analysis of the samples after mechanical milling, after hydrogenation at 623 K for 2 h, and after dehydrogenation at 623 K for 2 h was performed by X-ray diffraction (XRD) on a D/MAX-2500/PC diffractometer equipped with a Cu Kα radiation source
The sample of pure MgH2 only absorbs 0.53wt% H2 within the same time. These results clearly indicate that MgH2 catalyzed by NbH, LaH3, and LaH3 + NbH performs much better than pure MgH2 in both maximum hydrogen storage capacity and hydrogen absorption rate

Summary

Introduction

New energy resources have been eagerly sought because fossil fuels are being gradually exhausted and their combustion products pollute our environment [1,2]. Metal hydrides that provide high hydrogen storage capacity have been studied as promising materials over the past several decades. A β-/γ-MgH2 nanocomposite with enhanced hydrogen desorption kinetics was synthesized via a simple wet chemical route [28,29]. As previously discussed, both the La hydride and the Nb hydride can improve the hydriding and dehydriding properties of Mg-based hydrides. To enhance the hydriding/dehydriding kinetics and decrease the decomposition temperature of MgH2, we prepared a novel LaH3 and NbH co-doped MgH2 composite by mechanical milling and subsequently investigated the catalytic effects of LaH3 and NbH on the hydrogen desorption of an Mg-based hydride in detail

Experimental

Results and discussion

Determination of activation energy

Conclusions