Preparation and photo-fenton degradation activity of -Fe₂O₃ nanorings obtained by adding H₂PO₄^-, SO₄^2-, and citric acid

Improving the photocatalytic activity of alpha-Fe2O3 is crucial for the photo-Fenton degradation of organic pollutants. Herein, high-activity alpha-Fe2O3 nanorings were prepared via hydrothermal synthesis by adding H2PO4, SO42-, and citric acid. Analysis showed that spindle-shaped alpha-Fe2O3 particles were formed when only NaH2PO4 was added. Spindle-shaped alpha-Fe2O3 was dissolved along the c-axis to form hollow-structured products due to the coordination of SO42-. Small-sized citric acid-modified alpha-Fe2O3 nanorings with outer and inner diameters of approximately 60 nm and 30 nm, respectively, were obtained by adding a small amount of citric acid under the synergy of H2PO4-, SO42-, and citric acid. The as-prepared alpha-Fe2O3 nanorings with a high surface area can enhance visible light absorption, inhibit photo-induced electron and hole recombination, and increase surface-bound Fe(II) content. Consequently, catalytic activity in the photo-Fenton degradation of p-nitrophenol was increased.