Theoretical and experimental investigations related to electrolytic reverse complete oxidation within the sodium-boron-hydrogen-oxygen system

This work presents theoretical and experimental findings pertaining to the possible replacement of conventional, automotive fuels by solid, light alkaline-metal borohydrides (ΣM+,B 3+/H-). On a complete oxidation basis, and under certain arrangements, the latter fuels have volumetric energy capacities that exceed the most recognized, automotive constraints; furthermore, the solid metal oxide products (ΣM+,B3+/O2-) have the potential to be regenerated off-board to their respective hydrides via electrolytic reverse complete oxidation processes.;Electrolytic reverse complete oxidation processes are conceptualized as water electrolysis and electrolytic reverse combustion or electrolytic reverse hydrolysis unit operations in series. To more clearly express these mostly electrochemical fuel-cycles, a thermodynamic reaction model was contrived.;To investigate the electrolytic reverse hydrolysis hypothesis, attempts were made to prepare metal-supported, electrolytic reverse hydrolysis anode compartments. The glycine nitrate process facilitated the synthesis of nickel iron oxide (anode) and select doped ceria fluorite and double-doped LaGaO 3 perovskite (solid oxygen anion electrolytes) powders. Hydridic electrolyte compositions belonging to the Na2BH5-Na4B 2O5 quasi-binary system were synthesized from NaH, NaBH 4 and NaBO2. Analyses for the materials' compatibilities and solubilities studies (823 ± 10 °K, 1.00 ± 0.01 MPa) included induction coupled plasma, inert x-ray diffraction, and scanning electron microscopy.;NaH reduces magnetite to austenite; hence, the most promising solid oxygen anion electrolyte, La0.7Sr0.3Ga0.7Fe 0.3Mg0.1O3-δ (LSGFM), cannot be in direct contact with these hydridic electrolytes. The other oxides of La0.8Sr 0.2Ga0.8Mg0.2O3-δ are significantly soluble in these melts, but either a quenching or an electrochemical technique will be required to more accurately assess their values.;For the preparation of small, metal-supported, electrolytic reverse hydrolysis anode compartments, suspension plasma spraying was used for the depositions of the anode and solid oxygen anion electrolyte layers. Energy dispersive x-ray spectroscopy, scanning electron microscopy, and x-ray diffraction were used for the analyses of the resultant coatings' characteristics.;In consequence of LSGFM's remarkable specific conductivity at ∼ 673 °K, a solid oxygen anion electrolyte-supported, electrolytic reverse combustion or electrolytic reverse hydrolysis anode compartment design may be considered, but this will require the addition of a protective, solid oxygen anion electrolyte layer. The thermodynamic analyses has identified scandia stabilized zirconia as the most auspicious solid oxygen anion electrolyte; hence, understanding the nature of the anhydrous Sc 3+,Zr4+,B 3+,Na+,H+/H-,O 2- system at 723 ± 50 °K and ≤ 1.0 MPa is paramount to further efforts regarding electrolytic reverse hydrolysis or electrolytic reverse combustion proof-of-concept studies.;Keywords: hydrogen storage; molten salts; radio-frequency induction-coupled suspension-plasma-spraying; solid oxide electrolytes.