FISR project TEPSI:Nanostructured Mg for fast and reliable hydrogen deliveryFISR project TEPSI:Nanostructured Mg for fast and reliable hydrogen delivery

ABSTRACT: The tailoring of hydrogen sorption kinetics of Mg hydride represents one of the most challenging opportunities for a safe storage and reliable use of hydrogenin on board applications. The main technological limitations required for most applications, represented by the slow desorption kinetics at the too high desorptiontemperatures, can overcome by nanostructured hydrides and catalysts. By means the support of detailed characterization of both functional properties andmicrostructure [1,2], the aim of the TEPSI project is to study the effect of nanostructures on the performances of the Mg-based hydrides and to perform newcomplementary synthesis methods. In particular, Mg-based nanostructured materials (thin films or nanopowders) are prepared by (1) Sputtering techniques, a suitable

SPUTTERING TECHNIQUENb-doped Mg produced

by r.f. magnetron sputtering in the range of 6x10-4 < [Nb/Mg] < 5x10-2):

STRUCTURAL

and KINETIC ANALYSIS

TEM images

before and after

H2 sorption

cycling of Nb-

doped Mg:

the material

passes from a

micro-

to a nano-

structure

By the Sievert Apparatus

we study the sorption

performances

of the catalyzed materials

and determine the Activation

Energy and Rate Limiting

Step of the reaction

Lower Temperature!

EXAFS measurements

on Nb-doped Mg confirmed

the presence of Nb atomic

level clusters (~ 20nm) in as

deposited sample, the

presence of NbH in

hydrogenated samples and

their size reduction after the

desorption reaction

Nb-doped Mg

As-deposited Desorbed

Sample ττττ1/2 (sec)Ea (kJ mol-1) Rate Limiting Step

pure MgH23250±50 141±5 Nucleation

Mg + 0,006 at.% Nb 2390±50 140±5 Diffusion +

Nucleation

Mg + 1 at.% Nb 290±10 78±5 Diffusion +

Nucleation

Mg + 2-5 at.% Nb 110±10 51±5 Diffusion

Mg NANOPARTICLES by INERT GAS CONDENSATION:

DTA and H2 desorption curves of MgH2 with different Nb concentration; T: 623K

Faster Kinetics! Lower temperature!

Mg 0,02 mbar He Mg 2 mbar He

Typical TEM images of the Mg

nanoparticles prepared by IGC apparatus

at different He pressure associated to DSC

curves of the respective samples. By

decreasing the He pressure during the

synthesis process, the average

nanoparticles size decrease and the

desorption performances improve.

IGC

apparatus

SE 1kV

SE 20kV

BSE 20kV

An original method to study the

microstructure of Mg-MgH2

cross-sectional samples at high

spatial resolution has been set

up and successfully tested on

partially desorbed powders. The

method is based on the

difference in the electronic

structure between the two

phases which gives rise to a

contrast observable in low

voltage SEM images.

With Fe catalyst

well visible Mg-MgH2 phase

distribution in low energy SE

Catalyzing particles well

observed in high energy BSE

Complete microstructural

information by the

comparison of high energy

BSE and

low primary energy SE

We can observe mixed

microstructures extending

over almost the whole sample

Without catalyst:

Low energy SE is

able to reveal

microstructures

Images BSE confirm

the results

Charging artefacts in

high voltage SE

images

We observe a

coarse

microstructure and a

finer microstructure

at Mg /MgH2

interface

A.Montone1, A.Aurora1, C.Battaglin2, N.Bazzanella3, E.Bonetti4, R.S.Brusa3, E.Callini4, M.Celino1, R.Checchetto3, V.Contini1, S.Giusepponi1, G. Mattei5, C. Maurizio6, P. Mazzoldi5,

P.Mengucci7, A.Miotello3, M.R.Mancini1, D.Mirabile Gattia1 , L.Pasquini4, N.Patel3, E.Piscopiello1*, C. Sada 5, G. Siviero 5, M.Vittori-Antisari11ENEA, Dipartimento FIM, C.R.Casaccia, Via Anguillarese, 301, 00123 Roma; 1*ENEA, Dipartimento FIM, C.R.Brindisi, S.S. 7 “Appia”, Km 706, 72100 Brindisi; 2Dipartimento di Chimica Fisica, Università Ca’ Foscari di Venezia, Calle Larga S. Marta, 30100 Venezia;3Dipartimento di Fisica, Università degli Studi di Trento, 38050 Povo, Trento; 4Dipartimento di Fisica Università degli Studi di Bologna, v.le Berti Pichat 6/2, 40127 Bologna - 5Dipartimento di Fisica, CNISM, Università degli Studi di Padova, via Marzolo 8 , 35100Padova; 6ESRF, Grenoble (Francia); 7Dipartimento di Fisica ed Ingegneria dei Materiali e Territorio dell’Università Politecnica delle Marche, I-60131 Ancona, Italy

complementary synthesis methods. In particular, Mg-based nanostructured materials (thin films or nanopowders) are prepared by (1) Sputtering techniques, a suitablemethod for the synthesis of model materials where the properties can be easily correlated to the microstructure; (2) inert gas condensation, with the aim to study the finedetails of hydrogen uptake and release in 3D nano-sized model systems and (3) high energy ball milling which represents the main road for industrial scale-up.

[1] N. Bazzanella, R. Checchetto, A. Miotello, C. Sada, P. Mazzoldi, P. Mengucci,

Appl. Phys. Lett., 89, 1 (2006) 014101,

[2] A. Montone, J. Grbovic Novakovic, M. Vittori Antisari, A. Bassetti, E. Bonetti,

A.L.Fiorini, L. Pasquini, L.Mirenghi, P.Rotolo, Int. J. Hydr. Energy, 32, (2007) 2926

[3] A. Bassetti, E. Bonetti, L. Pasquini, A. Montone, J. Grbovic, M. Vittori Antisari, Eur

Phys. J. B, 43 (2005),19

DTA curves of MgH2 in different conditions

SE 1kV

SE 20kV

BSE 20kV

HIGH ENERGY BALL-MILLING:MgH2 with catalysing Fe particles

METALLOGRAPHIC ANALYSIS

FIRST PRINCIPLE CALCULATIONof MgH2 / Mg interface:

MONOSTRUCTURAL

CHARACTERIZATION AND H2 diffusion

MgH2 10h milled

with Fe catalyst

MgH2 10h milled

MgH

2Mg

Mg/MgH

2

As received

MgH2

Effect of

ball milling

Effect

ball milling+

Addiction of

Catalysts

Fe

Lower Temperature!