Densities, Viscosities, and Self-Diffusion Coefficients of Aqueous Mixtures of NaBH4, NaB(OH)4, and NaOH Using the BH4– Delft Force Field (DFF/BH4–)

One of the most promising energy carriers for transport applications are hydrogen-based energy carriers. NaBH4 is a hydrogen energy carrier and produces hydrogen bubbles when it is dissolved in water. The formation of hydrogen bubbles hinders experimental measurements of the thermodynamic and transport properties of aqueous NaBH4 solutions at elevated temperatures. Accurate knowledge of these properties is essential for the NaBH4 hydrolysis reactor modeling and design. Molecular dynamics (MD) simulations provide the option to study the thermodynamic and transport properties of NaBH4 aqueous solutions without hindering hydrogen bubble formation. In this work, a new force field is developed for BH4–, namely, the Delft force field of BH4– (DFF/BH4–), which, combined with additional force fields, can accurately describe experimental densities and viscosities of 0 to 5 m (mol salt/kg water) NaBH4, 0 to 3 m NaB­(OH)4, and 1 m NaOH aqueous solutions at 295 K within 1.8% and 10.8% maximum deviation, respectively. Empirical fitting correlations are created for densities, viscosities, and self-diffusivities obtained from the MD simulations of 0 to 5 m NaBH4, 0 to 5 m NaB­(OH)4, and 0 to 1 m NaOH aqueous solutions at 295–363 K for NaBH4 hydrolysis reactor modeling and design purposes.