Rapid hydrogen evolution from NaBH4 methanolysis using Co–Fe LDH: catalytic efficiency, kinetic modeling, and recyclability
摘要
This work explores the catalytic performance of Co–Fe layered double hydroxide (LDH) in the methanolysis of sodium borohydride (NaBH4) for hydrogen production. A systematic investigation was carried out to assess the influence of temperature (20–50 °C), catalyst loading (133–1333 ppm), methanol volume (5–20 mL), and NaBH4 concentration (0.176–0.881 M) on the hydrogen generation rate (HGR). The Co–Fe LDH catalyst was synthesized through co-precipitation and thoroughly characterized via X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDX), elemental mapping, Fourier-transform infrared spectroscopy (FT-IR), and Brunauer–Emmett–Teller (BET) techniques. Kinetic evolutions revealed a power-law rate model with a reaction order of 2.25 and an activation energy of 8.47 kJ mol−1. Additional kinetic modeling using Michaelis–Menten and Langmuir–Hinshelwood approaches yielded activation energies of 10.61 and 10.08 kJ mol−1, respectively. Thermodynamic analysis indicated favorable reaction conditions, with calculated enthalpy and entropy values of 14.20 kJ mol−1 and 39.45 kJ mol−1 K−1, and a progressive decrease in Gibbs free energy from − 11,543.6 to − 12,727.0 J mol−1. The optimum HGR value of 584.43 L min−1 gcat−1 was achieved at 30 °C using 133 ppm catalyst, 0.528 M NaBH4, and 15 mL methanol. Under identical conditions, except for a higher NaBH4 concentration of 0.881 M, the maximum HGR increased to 776.40 L min−1 gcat−1. After five successive reaction cycles, the catalyst preserved 91% of its initial activity, confirming its reusability and structural stability. These results underscore the potential of Co–Fe LDH as a low-cost, eco-friendly catalyst for rapid hydrogen generation, with promising implications for future enhancements.