Nanolayer-like-shaped MgFe2O4 synthesised via a simple hydrothermal method and its catalytic effect on the hydrogen storage properties of MgH2.

N A Ali,M S Yahya,M Ismail,Nurul Hayati Idris,N S Mustafa,M F Md Din,N A Sazelee,N N Sulaiman,F A Halim Yap

doi:10.1039/c8ra02168f

Abstract

In this study, the effect of nanolayer-like-shaped MgFe2O4 that is synthesised via a simple hydrothermal method on the performance of MgH2 for hydrogen storage is studied. MgH2 + 10 wt% MgFe2O4 is prepared by using the ball milling method. The MgFe2O4-doped MgH2 sample started to release H2 at approximately 250 °C, 90 °C and 170 °C lower than the milled and pure MgH2 respectively. At 320 °C, the isothermal desorption kinetic study has shown that the doped sample has desorbed approximately 4.8 wt% H2 in 10 min while the milled MgH2 desorbed less than 1.0 wt% H2. For isothermal absorption kinetics, the doped sample can absorb approximately 5.5 wt% H2 in 10 min at 200 °C. Meanwhile, the undoped sample absorbs only 4.0 wt% H2 in the same condition. The activation energy of 10 wt% MgFe2O4-doped MgH2 composite is 99.9 kJ mol−1, which shows a reduction of 33.1 kJ mol−1 compared to the milled MgH2 (133.0 kJ mol−1). X-ray diffraction spectra display the formation of new species which are Fe and MgO after dehydrogenation, and these new species are believed to act as the real catalyst that plays a crucial role in improving the sorption performance of the MgFe2O4-doped MgH2 system by providing a synergetic catalytic effect.

Highlights

IntroductionPrevious research has proved that catalyst based on ternary metal oxides greatly improved the hydrogen storage performance of MgH2.15,25–35 Zhang et al.[25] demonstrate that ferrite nanoparticles (MnFe2O4, ZnFe2O4, Mn0.5Zn0.5Fe2O4 and CoFe2O4) can greatly lower the decomposition temperature of MgH2
To prepare for the future and ensure global environmental viability, energy systems have to be reliable, clean, low cost, environmentally friendly and exible
X-ray photoelectron spectroscopy and X-ray diffraction (XRD) tests show that Fe0.872O and Mg2MnO4 phases take part as signi cant role in enhancing the dehydriding performance of MgH2

Summary

Introduction

Previous research has proved that catalyst based on ternary metal oxides greatly improved the hydrogen storage performance of MgH2.15,25–35 Zhang et al.[25] demonstrate that ferrite nanoparticles (MnFe2O4, ZnFe2O4, Mn0.5Zn0.5Fe2O4 and CoFe2O4) can greatly lower the decomposition temperature of MgH2. We showed in our previous study that MnFe2O4 synthesised via a simple hydrothermal method provides a remarkable effect in improving the hydrogen storage performance of MgH2.27 Interestingly, our result showed that Fe metal formed a er dehydrogenation instead of Fe0.872O species, as claimed by Li et al.[26] This variation paved the way for the debate. Paper on how ternary metal oxides, ferrites, work as catalysts in improving the hydrogen sorption performance of MgH2. Inspired by the role of active species that formed during the heating process in the MgH2-ternary metal oxides catalyst system, it is quite interesting to investigate the use of other ferrites (e.g. MgFe2O4) as catalysts to improve the hydrogen sorption performance of MgH2. In this work, MgFe2O4 was synthesised by using a simple hydrothermal method, and its catalytic effects on the hydrogen sorption performance of MgH2 were systematically studied. The possible catalysis mechanisms of MgFe2O4 in the sorption performances of MgH2 are discussed in this paper

Experimental details

Results and discussion

Conflicts of interest

Conclusion