Thermal evolution of solid-liquid equilibria in the quaternary system: NaBH4–NaBO2–NaOH–H2O

The rise of portable electronic devices, brings to the fore the crucial issues of power supply. The foreseeable evolution in functionalities and utilizations, as regards portable electronic devices, together with the introduction of novel electronic components, entail considerable changes in requirements, in terms of power consumption and autonomy [1]. A Hydrogen generator system by means of the hydrolysis of borohydrides is a promising technology for portable fuel cells [2-4]. To increase the energy density of this H2 generator system, the NaBH4 concentration has to be maximized. For this, one of the main challenges remains to increase the NaBH4 concentration of alkaline aqueous solution without drawbacks due to the by-products crystallization, NaBO2.yH2O, with the pseudo hydration degree y = 0, 1/3, 2/3, 2 and 4 [5]. Sodium hydroxide is added to the solution to limit the self-decomposition of NaBH4, thus stabilizing the system. The ultimate goal of this work is to describe the thermal evolution of solid-liquid equilibria in the quaternary system NaBH4–NaBO2–NaOH– H2O, which represents the mixture present during the hydrolysis reaction. To delimit the liquid single-phase domain in the quaternary system, an isopletic section has been defined considering a constant NaOH composition.