Faculté des sciences

Stability and decomposition of NaBH₄.

Martelli, Pascal ; Caputo, Riccarda ; Remhof, Arndt ; Mauron, Philippe ; Borgschulte, Andreas ; Züttel, Andreas

In: The Journal of Physical Chemistry C, 2010, vol. 114, no. 15, p. 7173-7177

We investigate the stability and hydrogen desorption of NaBH₄. Dynamic pcT (pressure, concentration, and temperature) measurements under constant hydrogen flows are used to determine thermodynamic parameters of reaction. From the van’t Hoff equation the enthalpy and entropy of reaction, −108 ± 3 kJ mol⁻¹ of H₂ and 133 ± 3 J K⁻¹ mol⁻¹ of H₂ released, are obtained,... Plus

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    Summary
    We investigate the stability and hydrogen desorption of NaBH₄. Dynamic pcT (pressure, concentration, and temperature) measurements under constant hydrogen flows are used to determine thermodynamic parameters of reaction. From the van’t Hoff equation the enthalpy and entropy of reaction, −108 ± 3 kJ mol⁻¹ of H₂ and 133 ± 3 J K⁻¹ mol⁻¹ of H₂ released, are obtained, respectively. This corresponds to a decomposition temperature of Tdec = 534 ± 10 °C at 1 bar of H₂. The decomposition thereby occurs in one step; i.e., only one plateau is visible in the pressure composition isotherms. Elemental Na is identified as the major solid component in the residue by X-ray diffraction. The experimental results are discussed on the basis of theoretical calculations using the density functional theory approach. Starting from the optimized structure of the cubic α-phase of NaBH₄, we discuss possible decomposition routes involving elemental Na and B as well as Na−H and Na−B binary compounds as residual products.