Iron-based Metal-organic gel-derived Ferric oxide Nanosheets for Photo-Fenton Degradation of Rhodamine B

Photocatalysts play an important role in industrial wastewater treatment. So far, the photocatalysts of photo-Fenton degradation of water pollutants include metal-organic frameworks, two-dimensional layered hydroxides, and transition metal oxides. Among them, transition metal oxides have become a research hotspot because of their easy availability of metal ions, stability and non-toxicity during degradation. In particular, ferric oxide (Fe2O3) has the advantages of wide visible light absorption range, good optical response and high thermodynamic stability, which is considered to be a promising semi-conductor photocatalyst. Herein, in this work, Fe2O3 of two morphologies, flakes (namely 300-Fe2O3 and 400-Fe2O3) and spheres (namely 500-Fe2O3 and 600-Fe2O3) were obtained by calcinating sheet-like iron-based metal-organic gel (Fe-MOG) synthesized with Fe3+ and 1,10-phenanthroline-2,9-dicarboxylic acid in one step at room temperature, and were used for photo-Fenton degradation of rhodamine B (Rh B). The crystal structure and optoelectronic properties of the as-prepared Fe2O3 were characterized by powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy elemental mapping (EDS), the UV-Vis diffuse reflectance spectra (UV-Vis DRS) and electrochemical impedance spectroscopy (EIS). Among them, 400-Fe2O3 with carbon skeleton structure exhibited excellent electron transport performance and high photogenerated charge separation efficiency, endowing it with remarkable catalytic activity. In addition, the existence of oxygen vacancy in 400-Fe2O3 promoted the formation of Fe2+, which was the key factor to enhance the photo-Fenton activity. 400-Fe2O3 could photocatalytically degrade 97.5% Rh B within 60 min under neutral conditions, and the degradation efficiency was retained 85.3% after five consecutive cycles. Under visible light irradiation, a part of the photogenic electron (e(-)) generated by 400-Fe2O3 reacted with O-2 to generate superoxide anion radical (center dot O-2(-)), the other part of e. reduced Fe3+ to Fe2+ in situ. Subsequently, Fe2+ can catalyze the decomposition of H2O2 into hydroxyl radicals (center dot OH), and participated in the photodegradation of Rh B together with center dot O-2(-). This work provides a new idea for the development and design of semiconductor photocatalysts with excellent catalytic activity.