Enhanced Visible-Light Absorption of Fe(2)O(3) Covered by Activated Carbon for Multifunctional Purposes: Tuning the Structural, Electronic, Optical, and Magnetic Properties

[Image: see text] Visible-light absorption is a critical factor for photocatalyst activity and absorption of electromagnetic (EM) interference application. The band gap of Fe(2)O(3) 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 Fe(2)O(3)–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 O(2) or H(2)O to produce OH and superoxide (O(2)(–)) radicals. These radicals move inside the molecule of the pollutant (methylene blue (MB)) to break up the bond, with the final products being H(2)O and CO(2). 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. Fe(2)O(3)–carbon is a multifunctional material for the green environment because of its electromagnetic interference absorption and photodegradation of wastewater.