Events
Time: 4:30 p.m.
Place: Materials for hydrogen storage – future perspectives?, Hurtigruten, Norway
Eugenio Pinatel, Department of Chemistry, University of Torino, Turino, Italy
Mauro Palumbo
Marcello Baricco, Dipartimento di Chimica IFM and NIS, Università di Torino, Turino, Italy
CALPHAD for Hydrogen Storage Materials
Eugenio Pinatel [1] , Mauro Palumbo [2] , Marcello Baricco [3]
[1] Dipartimento di Chimica and NIS, Università di Torino, Via P.Giuria 9
I-10125 TORINO (Italy) eugenio.pinatel@unito.it
[2] ICAMS, Ruhr University Bochum, Stiepeler Strasse 129
D-44801 BOCHUM (Germany) mauro.palumbo@rub.de
[3] Dipartimento di Chimica and NIS, Università di Torino, Via P.Giuria 9
I-10125 TORINO (Italy) marcello.baricco@unito.it
In order to be used for applications, the thermodynamics of a candidate hydrogen storage system should be suitable for hydrogen sorption close to room temperature and pressure. Recent studies have shown that, by mixing different hydrides, it is possible to promote the hydrogenation/dehydrogenation processes. On the other hand, small changes in composition allow a tailoring of thermodynamic parameters. So, knowledge of thermodynamic stability of hydrides is fundamental to study the hydrogenation/dehydrogenation processes. Moreover, thermodynamics and phase diagrams are useful to rationalize synthesis reactions of these compounds and to suggest possible alternative reaction routes. Finally, the availability of a description of the thermodynamics of the system allows an estimation of driving forces for phase transformations.
A full picture of the thermodynamic properties of a system can be obtained by the CALPHAD approach [1]. The goal is to obtain a description of the dependence of the free energy of all phases as a function of temperature, pressure and composition. The analytical description of the temperature dependence of free energy, enthalpy, entropy and specific heat is given by parametric expressions. The composition dependence can be described analytically by suitable models, such as the sublattice model, which contains interactions parameters. For high order systems, several interpolation approaches have been suggested and, if necessary, high order interaction parameters can be introduced.
The interaction parameters are obtained by a least square procedure, starting from experimental values of existing phase diagrams and thermodynamic data. The base of the CALPHAD method is the availability of thermochemical data related to the investigated systems. In absence of experimental information, the output of various thermodynamic or quantum mechanical models can be used [2]. In particular, an estimation of the energy of formation of a compound can be obtained by ab-initio calculations. In fact, density Functional Theory (DFT) has proven to be very reliable when applied to predict structures and energetics of materials at the atomistic scale. A scheme of the CALPHAD approach is reported in figure 1.
The purpose of this work is to develop a consistent thermodynamic database for hydrogen storage systems by the CALPHAD approach. Experimental data have been collected form the literature. In absence of experimental information, an estimation of the energy of formation of hydrides has been obtained by ab-initio modelling.
The La-H and La-Ni-H phase diagrams have been reviewed and thermodynamically assessed [3]. Extension to Al-La-Ni-H system will be discussed. Al, Li, Mg, Na, B-containing compounds/systems of interest for hydrogen storage will be considered [4-6]. In particular, a CALPHAD assessment of LiBH4 will be presented [7]. The effect on thermodynamic properties of halide-to-hydrogen substitution in simple hydrides and in borohydrides will be presented [8,9]. Calculated and experimental thermodynamic properties have been compared and a satisfactory agreement has been achieved.
[1] B. Sundman, S.G. Fries and H.L. Lukas: Computational Thermodynamics (Cambridge 2007).
[2] P.E.A. Turchi, I.A. Abrikosov, B. Burton, S.G. Fries, G. Grimvall, L. Kaufman, P. Korzhavyi, V.R. Manga, M. Ohno, A. Pisch, A. Scott and W. Zhang: CALPHAD 31 (2007) 4.
[3] M. Palumbo, J. Urgnani, D. Baldissin, L. Battezzati, M. Baricco, Calphad 33 (2009) 162.
[4] J.Urgnani, F.J.Torres, M.Palumbo, M.Baricco, Int. J. Hydr. Ener. 33 (2008) 3111.
[5] M. Palumbo, F. J. Torres, J. R. Ares , C. Pisani, J. F. Fernandez, M. Baricco, Calphad 31 (2007) 457.
[6] D.Pottmaier, E.R.Pinatel, J.G.Vitillo, S.Garroni, M.Orlova, M.D.Baró, G.B.M.Vaughan, M.Fichtner, W.Lohstroh, M.Baricco, Chem. Mater. 23 (2011) 2317.
[7] A.El Kharbachi, E.Pinatel, I.Nuta, C.Chatillon, M.Baricco, submitted to J. Chem. Thermod.
[8] J.E.Fonneløp, M.Corno, H.Grove, E.Pinatel, M.H.Sørby, P.Ugliengo, M.Baricco, B.C.Hauback, J. Alloy. Comp. 509 (2011) 10.
[9] O.Zavorotynska, L.Rude, M.Corno, E.Pinatel, P.Ugliengo, T.Jensen, M.Baricco, Crystals 2 (2012) 144.
