Reaction of NaBH4 and NaB(OH)4 as a way to increase the yield of hydrogen in catalytic hydrolysis of sodium borohydride by water

• Published in: Fuel (Guildford) Vol. 363; p. 130984
• Main Authors: Solovev, Mikhail V., Malkov, Georgiy V., Reveguk, Anastasiia A., Antonenko, Anastasiia O., Elets, Dmitriy I., Maystro, Alexey S., Yu. Buldakov, Pavel, Dobrovolsky, Yuriy A., Shihovtsev, Alexey V., Tsvetkov, Maxim V., Kravchenko, Oleg V.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.05.2024
• Subjects: Hydrides; Hydrogen; Hydrogen storage; Hydrolysis; Sodium borohydride; Hydrolysis; Hydrogen storage; Hydrides; Sodium borohydride; Hydrogen
• ISSN: 0016-2361
• DOI: 10.1016/j.fuel.2024.130984

•Mixtures of NaB(OH)4, NaBH4 and a Co-catalyst produce hydrogen at 70 °C and above.•Reaction regime of NaBH4 hydrolysis to low-water products is found.•At H2O:NaBH4 = 3 catalytic hydrolysis process results in 8.3 wt% the hydrogen yield.•Potential mass yield of hydrogen in the process can reach up to 9.3 wt%. In this work, sodium tetrahydroxoborate (NaB(OH)4) that is the main product of the hydrolysis reaction of NaBH4 with a relatively small excess of water is studied in the reaction with sodium borohydride in the presence of a catalyst and without it. It was found, that mixtures consisting of NaB(OH)4 and NaBH4 begin to melt at 70 °C with the formation of a liquid phase without destroying the close coordination environment for both types of boron atoms. When a cobalt-based catalyst is added to mixtures, significant hydrogen evolution is observed. The resulting products are hydrogen and amorphous borates with a gross composition close to [NaBO2·0.75H2O]. Carrying out the catalytic hydrolysis of borohydride in the system of initial composition H2O:NaBH4:catalyst under the conditions same to that the catalytic reaction of NaBH4 and NaB(OH)4 was observed is a promising way to produce H2 since it provides a high yield of hydrogen at small amounts of catalyst and atmospheric pressure. Catalytic hydrolysis carried out in the temperature range 80–120 °C with initial molar ratios H2O:NaBH4 = 3 and 2.7, and atmospheric pressure demonstrates a hydrogen yield of 8.3 wt% and NaBH4 conversion of 96 % at only 2.3 wt% of CoCl2 as catalyst. Since the resulting final composition of borates is close to [NaBO2·0.66H2O], the potential mass yield of hydrogen in this process can reach 9.3 wt%.