High-efficient synthesis of NaBH₄ by solid-phase electrolysis process on a core-shell-type cathode

NaBH4 is a promising hydrogen storage material, while faced with enormous difficulties for scale-up application due to regeneration issues. In this study, a highly efficient and economical strategy for the electrosynthesis of NaBH4 from hydrolysis by-product NaB(OH)(4) has been proposed. By fabricating solid-phase electrodes with NaB (OH)(4) and electrocatalyst etc., the mass transfer process of B(OH)(4)(-) at the cathode surface was remarkably improved, thus reducing the resistance of the cathodic reaction. Meanwhile, XPS, FTIR, and CV analyses were combined to reveal the reaction path and control steps of B(OH)(4)(-) reduction to BH4- in the electrocatalytic system. The formation of NaBH4 and intermediates (BH(OH)(3)(-) , BH2(OH)(2)(-), and BH3(OH)(-)) is the gradual replacement of (OH)(-) in NaB(OH)(4) by H- . Furthermore, this study reveals that PbO has a suitable hydrogen evolution overpotential and excellent selective catalytic activity. The current efficiency for NaBH4 synthesis via solid-phase electrolysis was up to 68.12 % by systematically regulating various factors.