Benzoic acid-functionalized bismuth nanowires: Synthesis, characterization, and catalytic role in hydrogen generation via sodium borohydride methanolysis

Benzoic acid-functionalized bismuth nanowires (BzOH-Bi NWs) were synthesized using a solvothermal chemical reduction method, where benzoic acid (BzOH) reacted with bismuth nitrate pentahydrate (Bi(NO₃)₃·5H₂O) in dimethylformamide (DMF) at 110 °C. In this approach, benzoic acid served a dual role: it acted as a reducing agent, converting Bi³⁺ ions to metallic Bi⁰, and as a stabilizing or capping agent, preventing the agglomeration of the nanowires. The resulting BzOH-Bi NWs were characterized using several techniques: X-ray diffraction (XRD) to determine their crystal structures, Fourier-transform infrared spectroscopy (FTIR) to identify molecular bonds and functional groups, scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM-EDX) to assess elemental composition and morphology, and X-ray photoelectron spectroscopy (XPS) to investigate their chemical oxidation states. These BzOH-Bi NWs were then tested as catalysts in the sodium borohydride (NaBH₄) methanolysis reaction for hydrogen production. The BzOH-Bi NWs exhibited exceptional catalytic activity, achieving a hydrogen production rate (HPR) of 42.32 L/min.g_catalyst when using 5 mg of BzOH-Bi NWs, 125 mg of NaBH₄, and 4 mL of methanol at 30 °C. The activation energy of the reaction was calculated to be 18.6 kJ/mol using the Arrhenius equation. Furthermore, the catalysts demonstrated excellent reusability, maintaining high performance over 5 cycles, highlighting their potential as highly effective catalysts for hydrogen generation.