Within the last decade, the development of environmental and economically viable fuel cell technology has come in response to the push to decrease the use of fossil fuels. Current fuel cell technology has lacked in the fueling of the cell with a viable hydrogen source. Materials with a high hydrogen weight percent, such as sodium borohydride (NaBH4, 10.8% wt), provide a viable source in the presence of a metal catalyst. Metal organics frameworks (MOFs) have seen an exponential growth in interest for industrial applications such as catalysis, filtrations and storage.¹ Their use as catalysts for the hydrolysis of hydrogen feedstock materials has the potential to improve current fuel cell technology by providing a metal catalyst with a high surface area. In this study, NiCl₂• 6H₂O was coordinated to the organic ligands of disodium terephthalate (C₈H₄Na₂O₄ (Na₂BDC)) to synthesize the nickel terephthalate complex (Ni-MOF) in an aqueous media.³ The Ni-MOF was synthesized at room temperature (RT), with crystal formation occurring instantly, a highly desirable time frame for industrial applications.³ The catalytic efficiency of the Ni-MOF catalyst was also tested in aqueous solution with the hydrogen feedstock material, NaBH₄, in varying conditions of pH, temperature and concentration.^1,4 These efficiencies were compared to the catalytic capabilities of NiCl₂ • 6H₂O as a reducing catalyst. The Ni-MOF was characterized via surface area analysis for surface area and pore volume, powdered x-ray diffraction (PXRD) for crystallization, thermogravimetric analysis (TGA) for thermo-stability and scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) to determine the chemical composition of the framework. The hydrolysis of NaBH₄ via the Ni-MOF showed an overall increase in hydrogen volume produced and production rate over the metal-salt catalyst. Increased volumes of 43.56 mL to 70.03 mL were seen for the MOF at 303 K and similar increases for each of the other temperature trials as well as variation to pH of solution. Increases were also seen for the activation energy of the catalysts from 56.23 kJ mol^-1 to 62.55 kJ mol^-1 when coordinated into the nickel framework. Through TGA analysis the framework was found to be stable up to 620 K. Overall, the synthesis of Ni-MOF from NiCl₂ • 6H₂O and disodium terephthalate, provides an easy synthesis that increases the catalytic efficiencies while maintaining green chemistry properties.

References

1. Huff C., Long J., Aboulatta A., Heyman A., Abdel-Fattah T.M., ECS Journal of Solid State Science and Technology (2017), 6 (10), M115-M118
2. Schlesingehr H.I.; Brown, H.C.; Finholt A.E.; Gilbreath J.R.; Hoekstra H.R.; Hyde E.L.; Sodium Borohydride, Its Hydolysis and its Use as a Reducing Agent in the Generation of Hydrogen; Am. Chem. Soc., (1953), 75 (1), pp 215–219
3. Sánchez-Sánchez M., Getachew N., Díaz K., Díaz-García M., Chebudeb Y., Díaz I.; Green Chem., 17, 1500–1509 (2015)
4. Walter, J.C.; Zurawski, A.; Montgomery, D.; Thornburg, M.; Revankar, S.; Sodium borohydride hydrolysis kinetics comparison for nickel, cobalt, and ruthenium boride catalysts; of Power Sources 179 (2008) 335–339