Boosting Catalytic Dye Degradation in Fe2O3 Nanozyme through Cu-Doping Mediated Phase Transformation

A dual-phase copper-doped iron oxide nanozyme (Cu-α/γFO) was synthesized via a facile hydrothermal method for efficient organic pollutant degradation. The as-prepared Cu-α/γFO exhibits excellent peroxidase-like activity, degrading 99.5% rhodamine B (RhB) under optimal conditions (pH 4, 40°C) while retaining 40.73% of its initial activity after three cycles. Critically, it demonstrates broad-spectrum catalytic efficacy, efficiently degrading diverse organic dyes (e.g., cresol red, methyl violet, methylene blue), and retains high catalytic activity even in complex environments containing coexisting cations (K⁺, Ca²⁺, Mg²⁺), anions (H₂PO₄⁻, HCO₃⁻, NO₃⁻), or organic solvents (acetone, ethyl acetate). X-ray diffraction (XRD) and Raman spectroscopy confirmed the Cu-doping-induced α/γ-Fe₂O₃ phase crystal structure, while minimal copper leaching after 21-day aqueous storage validated structural integrity. The mechanism of enhanced peroxidase-like activity of Cu-α/γFO was proposed based on integrated characterization, including electron spin resonance (ESR), electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and density of states calculations. Degradation pathways were elucidated using high-performance liquid chromatography-mass spectrometry (HPLC-MS) identification of intermediates and theoretical calculations. This work presents a dual-phase engineering strategy through targeted metal doping, advancing high-performance nanozymes for sustainable environmental remediation.