Mg-H dissociation of magnesium hydride MgH2 catalyzed by 3d transition metals

Thin Solid Films Muneyuki Tsuda, Wilson Agerico Diño, Hideaki Kasai, Hiroshi Nakanishi and Hiroshi Aikawa

vol 509 157-159 2006 　

YOSHIDA Lab.　

Ryusuke Tominaga

Contents

Introduction• The purpose of the research • The method to solve the problem• Hydrogen Absorbing Materials

The design of Hydrogen Absorbing Materials

summary

The purpose of research

• The purpose of the research is through creating high-quality hydrogen absorbing materials , to encourage the prevalence of fuel-cell electric vehicle , and thereby to contribute to the solving of the energy and environment concern .

fuel-cell electric vehicle「ＰＵＹＯ」

出典： http://www.nikkei.co.jp/news/main/im20071009AS1D0904609102007.html

（（ ->) ->) environment concern ②The efficiency of fuel-cell electric vehicle

is about 2 times more efficient than that of normal vehicle

(->energy concern)(->energy concern)

　　　　 　① No emissions of carbon dioxide

The hierarchy of industrial structureThe hierarchy of industrial structure

materialmaterial

devicedevicedevicedevice

　　 SystemSystem　　 SystemSystem

The change of industrial structure

Computational Nano Materials Design

The hierarchy of industrial ctructureThe hierarchy of industrial ctructure

Hydrogen Absorbing Materials Hydrogen Absorbing Materials

Fuel cellFuel cell

fuel-cell electric vehicle

fuel-cell electric vehicle

The change of industrial structure

Computational Nano Materials Design

What are the Hydrogen Absorbing Materials ?

　 The Hydrogen Absorbing Materials are the materials that can absorb and emit hydrogen.

The discover ： the 　 Philips Eindhoven institution

（ Netherlands) 　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　

The condition that must be satisfied to be a practical Hydrogen Absorbing system

①Can the system contain enough fuel for about 480km drive ranges at one time refilling ? -> over 6 (wt%)

②Can it release enough hydrogen to provide the power and acceleration that driver expects at about 350(K) ?

　　　

The examples of Hydrogen Absorbing Materials

• Chemical hydrides

• Compressed hydrogen

• Liquid hydrogen

• Hydrogen adsorbents

• Complex hydrides

http://www.eerj.co.jp/jp/Reference/Reference20070803/images/ExtractScientificAmericanJ.pdf

Specific material

• MgH2

Mg-H dissociation of magnesium hydride MgH2 catalyzed by 3d transition metals

Thin Solid Films

Muneyuki Tsuda, Wilson Agerico Diño, Hideaki Kasai, Hiroshi Nakanishi and Hiroshi Aikawa vol 509 157-159 2006 　

MgH2

• Hydrogen capacity :7.66 wt%

-> ( the condition :① over 6 (wt%) )

• H2 desorption temperature :700K

-> ( the conditon : ②About 350(K) )

The used model

Fig. 1. MgH2 + M (M: Sc to Zn) configurations with C2v symmetry. We put the M atom on top of the Mg of the MgH2.

The calculation condition

• Gaussian03 is used.

• M: Sc - Zn

• DFT

• B3pW91 6-31G(d,p)

• LANL2DZ

Calculated potential energy curves

Fig. 2. Calculated potential energy curves for the MgH2 + M (M: Sc to Zn) systems in Fig. 1 as a function of the Mg–H distance. In these calculations, the Mg–M distance is allowed to relax. The potential energies are defined as the energies required to increase the Mg–H distance from their equilibrium positions.

Calculated H2 desorption temperatures (Redhead’s equation)

Fig. 3. Calculated H2 desorption temperatures as a function of the activation barrier for the Mg–H bond cleavage.

summary

• H2 desorption temperature ->

700 K (no M) -> 500 K (with Sc or Ni)

• To be a practical Hydrogen Absorbing Materials , the H2 desorption temperature should be about 350 (K) .

• The further research is needed in order to weaken the Mg-H bond of MgH2.