Adrian Nur, Arif Jumari, Muhammad Dani Supardan, Nazriati, Zidan Insa Fauzi, Reza Pratama Aditia, Setiana Handayani, Arvian Raditya Airlangga
Sodium borohydride (NaBH4) is a high-hydrogen-content chemical hydride, but its practical use requires an efficient regeneration route from the hydrolysis by- product (NaBO2·2H2O). This work investigates a two-step NaBH4 - H2 cycle comprising catalytic hydrogen release and electrochemical regeneration of NaBH4. A Ni- Co/hydroxyapatite (HAp) catalyst was synthesized by an electrochemical one-step deposition route (160 mA cm-2, 90 min). The catalyst shows nano-sized primary particles (10- 100 nm) agglomerated into 1- 5 μm secondary clusters. The results of catalyst characterization with FTIR confirmed the presence of HAp with additional peaks indicating surface carbonaceous species. XRD of the catalyst identifies a composite of HAp with oxidized Ni/Co phases (NiCo2O4 and CoO), evidencing successful incorporation of Ni- Co active phases on the HAp support. Mechanistically, the Ni/Co oxide surface is expected to provide hydrogen-activation (H∗ formation) and borate adsorption sites, while HAp enhances dispersion and interfacial hydroxyl/phosphate functionality-together facilitating the hydrogenation of NaBO2 2H2 O toward NaBH4 when H2 is supplied electrochemically. In this work, NaBH4 was first hydrolyzed in water using an electrochemically synthesized Ni- Co/hydroxyapatite catalyst to release H2 and form borate, and the spent solution was then regenerated electrochemically in a two- chamber cell separated by a bipolar membrane. In- situ hydrogen generated via cathodic water reduction was utilized to convert NaBO22H2O back to NaBH4. Regeneration was evaluated at current densities of 0.10- 0.20 A cm-2 for up to 120 min. NaBH4 concentration increased with both electrolysis time and current density, reaching ∼0.020 mol L-1 at 0.20 A cm-2 after 120 min (compared with ∼0.017 0.10 A cm-2). These results demonstrate the feasibility of coupling hydrogen release and electrochemical regeneration in a closed. © 2026 The Authors, published by EDP Sciences.
Departement of Chemical Engineering, Universitas Sebelas Maret, Surakarta, Indonesia; Department of Chemical Engineering, Universitas Syiah Kuala, Banda Aceh, Indonesia; Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Negeri Malang, Indonesia
