Enhanced Visible-Light Absorption of Fe2O3Covered by Activated Carbon for Multifunctional Purposes: Tuning the Structural, Electronic, Optical, and Magnetic Properties

Abstract

Visible-light absorption is a critical factor for photocatalyst activity and absorption of electromagnetic (EM) interference application. The band gap of Fe₂O₃ is 2 eV, which can be increased by doping with a high-band-gap material such as carbon from activated carbon (AC) with a band gap of 4.5 eV for increased visible-light absorption. The porosity decreases from 88 to 81.6%, and the band gap increases from 2.14 to 2.64 eV by increasing the AC from 10 to 25%, respectively. The photocatalytic activity takes 120 min to produce a harmless product for 10-20% AC, but 25% AC shows 89.5% degradation in only 90 min and the potential to attenuate the EM wave up to 99% due to the RL being below -20 dB. The second- and third-cycle degradation achieved by the composite Fe₂O₃-AC having 25% AC is 88.2 and 86.5% in 90 min, respectively. The pore of the surface state of AC contains a trapped charge, and interaction occurs between the charge (electron/hole) and O₂ or H₂O to produce OH and superoxide (O₂ ^-) radicals. These radicals move inside the molecule of the pollutant (methylene blue (MB)) to break up the bond, with the final products being H₂O and CO₂. The X-ray photoelectron (XPS) spectra show that oxygen plays a key role in the interatomic bonding with Fe, C, and MB atoms. The best absorption of EM interference is -21.43 dB, with degradation reaching 89.51% in only 90 min for 25% AC due to its higher band gap and anisotropy constant. Fe₂O₃-carbon is a multifunctional material for the green environment because of its electromagnetic interference absorption and photodegradation of wastewater.

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