{Fe²⁺-imidazole} catalyst grafted on magnetic {Fe@Graphitized C} nanoparticles: a robust hybrid-catalyst for H₂ production from HCOOH

A novel hybrid-catalyst was synthesized via covalent grafting of a molecular catalyst {Fe²⁺-Imidazole} on magnetic core-shell {Fe@Graphitized C, Fe@GC} nanoparticles synthesized via anoxic flame spray pyrolysis (A-FSP). Transmission electron microscopy (TEM) shows that A-FSP produces a fine C-shell consisting of few graphitized layers, where {Fe²⁺-Imidazole} is covalently grafted. The hybrid catalyst {Fe²⁺-Imidazole}@{Fe@GC} demonstrated highly efficient H₂ production from formic acid (HCOOH) at near-ambient conditions of P = 1 atm and T = 80 °C, yielding >37 Liters of high-purity H₂ and a high turnover-number (TON) of >203 000. The {Fe²⁺-Imidazole}@{Fe@GC} catalyst could be easily and efficiently recovered magnetically and reused for at least 12 catalytic cycles, demonstrating significant durability and reusability. Raman, FT-IR, TEM and XRD confirmed the preservation of key structural features of the hybrid catalyst, despite prolonged exposure to reaction conditions. We attribute these beneficial characteristics to the robustness of the FSP-made nanographitized layers and the enhanced efficiency of the {Fe-Imidazole} catalyst when interfaced with nanocarbon.