Polymerization-Induced Colloid Assembly Route to Iron Oxide-Based Mesoporous Microspheres for Gas Sensing and Fenton Catalysis

Abstract

Iron oxide materials have wide applications due to their special physicochemical properties; however, it is a great challenge to synthesize mesoporous iron oxide-based microspheres conveniently and controllably with high surface area, large pore volume, and interconnected porous structures. Herein, mesoporous α-Fe₂O₃-based microspheres with high porosity are synthesized via a facile polymerization induced colloid assembly method through polymerization of urea–formaldehyde resin (UF resin) and its simultaneously cooperative assembly with Fe­(OH)₃ colloids in an aqueous solution, followed by subsequent thermal treatment. Remarkably, by controlling the cross-linking degree of UF, pure mesoporous α-Fe₂O₃ and α-Fe₂O₃/carbon hybrid microspheres can be synthesized controllably, respectively. They exhibit a uniform spherical morphology with a particle size of around 1.0 μm, well-interconnected mesopores (24.5 and 8.9 nm, respectively), and surface area of 54.4 m²/g (pure mFe₂O₃ microspheres) and 144.7 m²/g (hybrids), respectively. As a result, mesoporous pure α-Fe₂O₃ microspheres exhibited excellent H₂S sensing performance with a good selectivity, high response to low concentration H₂S at 100 °C, and quick response (4 s)/recovery (5 s) dynamics owing to the high surface area, open mesopores, and crystalline structure of the n-type α-Fe₂O₃ semiconductor. Moreover, mesoporous α-Fe₂O₃/carbon hybrid microspheres were used as a novel Fenton-like catalyst for the decomposition of methylene blue in a mild condition and exhibit quick degradation rate, high removal efficiency (∼93% within 35 min), and stable recycling performance owing to the synergetic effect of a high surface area and the carbon-protected α-Fe₂O₃