CO2-Assisted Hydrolysis of NaBH4: A Multi-Function Platform for Enhanced Hydrogen Release, Regeneration of NaBH4, and CO2-to-CH4 Conversion.

Sodium borohydride (NaBH4) is a promising hydrogen storage material due to its high hydrogen content and facile high-purity hydrogen release via hydrolysis. This work reports that carbon dioxide (CO2) accelerates the hydrolysis of NaBH4 and facilitates the regeneration of NaBH4 via ball milling the hydrolytic products with Mg. CO2 significantly enhances the hydrogen release by providing protons required during hydrolysis. It also facilitates the formation of borax during hydrolysis which can be used directly as feedstocks to regenerate NaBH4 with a high yield of over 76%. Compared to widely used metal-based catalysts, CO2-assisted hydrolysis offers significant advantages since it eliminates the need for metal catalyst separation from the hydrolytic products, simplifying recovery and enabling more efficient NaBH4 regeneration. Moreover, CO2 is converted to CH4 during the process, achieving both carbon capture and conversion. This multi-functional approach contributes to the development of a closed-loop hydrogen storage system, accompanied by an efficient CO2 conversion to a power fuel.