CO ₂ ‐Assisted Hydrolysis of NaBH ₄ : A Multi‐Function Platform for Enhanced Hydrogen Release, Regeneration of NaBH ₄ , and CO ₂ ‐to‐CH ₄ Conversion

ABSTRACT Sodium borohydride (NaBH ₄ ) 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 (CO ₂ ) accelerates the hydrolysis of NaBH ₄ and facilitates the regeneration of NaBH ₄ via ball milling the hydrolytic products with Mg. CO ₂ 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 NaBH ₄ with a high yield of over 76%. Compared to widely used metal‐based catalysts, CO ₂ ‐assisted hydrolysis offers significant advantages since it eliminates the need for metal catalyst separation from the hydrolytic products, simplifying recovery and enabling more efficient NaBH ₄ regeneration. Moreover, CO ₂ is converted to CH ₄ 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 CO ₂ conversion to a power fuel.