Tunable Synthesis of Hematite Structures with Nanoscale Subunits for the Heterogeneous Photo-Fenton Degradation of Azo Dyes

Facile syntheses of branched hematite (α-Fe₂O₃) crystals with fine-tuning of their nanoscale subunit morphologies were reported. Starting from Prussian red and bisolvent systems with controlled temperature as the crucial parameters, fine-tuning of the nanoscale subunit morphologies in the context of controlling the anisotropic growth of branched α-Fe₂O₃ crystals was demonstrated. The systematic and optimized studies significantly improved the controlled synthesis of the hierarchical growth of nanoscale subunits, leading to the formation of branched dendritic leaflike (secD₃D, tertD₂D, and tertD₃D) and hyperbranched (secS₂D and hypB₂D) α-Fe₂O₃ particles for their size-reduced variants used in photocatalysis. The kinetics of the photo-Fenton degradation of three azo dyes (chlorazol black, direct blue, and methyl orange) with five types of branched dendritic α-Fe₂O₃ particles were compared systematically.