Abstract

The influence of transition metal oxide catalysts (ZrO2, CeO2, Fe3O4 and Nb2O5) on the hydrogen desorption kinetics of MgH2 was investigated using constant pressure thermodynamic driving forces in which the ratio of the equilibrium plateau pressure (pm) to the opposing plateau (pop) was the same in all the reactions studied. The results showed Nb2O5 to be vastly superior to other catalysts for improving the thermodynamics and kinetics of MgH2. The modeling studies showed reaction at the phase boundary to be likely process controlling the reaction rates of all the systems studied.

Highlights

  • IntroductionMagnesium hydride has received considerable attention as a promising hydrogen storage material for on-board vehicular applications because of its high theoretical hydrogen storage capacity (7.6 wt%)

  • Magnesium hydride has received considerable attention as a promising hydrogen storage material for on-board vehicular applications because of its high theoretical hydrogen storage capacity (7.6 wt%)and high volumetric density (110 g/L) as well as low cost

  • Temperature Programmed Desorption (TPD) measurements were done on several ball milled mixtures of MgH2 with 4 mol% of Nb2O5, ZrO2, CeO2 and Fe3O4

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Summary

Introduction

Magnesium hydride has received considerable attention as a promising hydrogen storage material for on-board vehicular applications because of its high theoretical hydrogen storage capacity (7.6 wt%). Investigated the influence of metal oxides such as Sc2O3, TiO2, V2O5, Cr2O3, Mn2O3, Fe3O4, CuO, Al2O3 and SiO2 on the hydrogen sorption behavior of MgH2 They found that the composite material containing Fe3O4 showed the fastest desorption kinetics. It is very important that this be done because without constant pressure driving forces, results will vary largely as the conditions change The importance of this unique method was first demonstrated by Goudy and coworkers [13,14,15] when they analyzed the kinetic behavior of a series of LaNi5-based intermetallic hydrides. An attempt has been made to compare the intrinsic dehydriding kinetics of MgH2 ball milled with various transition metal oxides using constant pressure thermodynamic driving forces. The results should provide more insight into the role that catalysts may have on reaction temperature and rates

Experimental Section
Temperature Programmed Desorption Measurements
Programmed Composition Isotherm Measurements
Kinetics Measurements
Kinetics Modeling Studies
Differential Thermal Analysis and Kissinger Plots
Conclusions

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