Iron Nitride‐Derived In Situ <i>N</i> ‐doped Fe ₂ O ₃ Nanoaggregates with Optimized Band Structure for Solar‐Driven Photocatalytic Water Splitting

This study presents a facile strategy for synthesizing in situ N-doped Fe₂O₃ from iron nitride to tune its band structure for photocatalytic applications. XRD analysis confirms the structural formation α-Fe₂O₃, while XPS analysis verifies nitrogen incorporation of 8.87% and 5.52% in N-doped Fe₂O₃ obtained by oxidizing iron nitride at 450 °C and 550 °C, corresponding to high-doped and low-doped Fe₂O₃ (HD-FO and LD-FO) systems. FESEM and BET analysis showed that N-doping influenced particle aggregation, surface area, and porosity, with bare Fe₂O₃ (FO) exhibiting the highest surface area (43.9 m²/g), followed by HD-FO (34.39 m²/g) and LD-FO (25.79 m²/g). UV-vis and valence band XPSs revealed bandgap narrowing from 2.80 eV (FO) to 2.71 eV (LD-FO) and 2.53 eV (HD-FO), improving visible light absorption. Mott-Schottky plots showed more negative conduction band potentials for LD-FO (-0.46 eV) and HD-FO (-0.54 eV compared to FO (-0.39 eV), indicating enhanced electron transfer properties in the systems. Photocatalytic RhB degradation under sunlight achieved ∼97%, 90%, and 87%, and H₂ production rates of 839.6, 749.4, and 656.9 µmol g^-1 h^-1 for LD-FO, HD-FO, and FO, respectively. The results highlight the efficacy of iron nitride as a precursor for the in situ doping of N in Fe₂O₃ for efficient photocatalytic applications.