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. 2021 Oct 18;6(42):28334-28346.
doi: 10.1021/acsomega.1c04526. eCollection 2021 Oct 26.

Enhanced Visible-Light Absorption of Fe2O3 Covered by Activated Carbon for Multifunctional Purposes: Tuning the Structural, Electronic, Optical, and Magnetic Properties

Dahlang Tahir  1 , Sultan Ilyas  1 , Roni Rahmat  1 , Heryanto Heryanto  1 , Ahmad Nurul Fahri  1 , Mufti Hatur Rahmi  2 , Bualkar Abdullah  1 , Chol Chae Hong  3 , Hee Jae Kang  4
Affiliations

Enhanced Visible-Light Absorption of Fe2O3 Covered by Activated Carbon for Multifunctional Purposes: Tuning the Structural, Electronic, Optical, and Magnetic Properties

Dahlang Tahir et al. ACS Omega. .

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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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
Illustration of the mechanism for enhancing visible-light absorption by varying the amount of activated carbon (AC). When the EM wave enters the material, the interaction occurs with the atoms, and the energy spreading into the small waves produces vibration of the atoms and the lattice structure, and some of the energy is converted to thermal energy.
Figure 2
Figure 2
Proposed photodegradation process. The photon energy absorbed by the electron in the valence band moves to the conduction band; the remaining hole, which goes to the surface of the material, is captured by the magnetic pore for generating OH and the superoxide anion radical (O2–) via photoelectrochemical decomposition of the H2O and O2 molecules for breaking the chemical structure of the pollutant, finally giving a harmless product.
Figure 3
Figure 3
(a) X-ray diffraction (XRD) full spectrum, (b) enlarged diffraction peaks (104) and (110), and (c) Fourier transform infrared (FTIR) spectra for the composite Fe2O3–carbon as a function of the amount of carbon. We have included ICDS 98-008-8414 for comparison.
Figure 4
Figure 4
(a) Scherrer and (b) size strain plot (SSP) methods for the analysis of the XRD spectra in Figure 3a. Optical properties: (c) refractive index (n) and extinction coefficient (k), and (d) the real (ε1) and imaginary parts (ε2) of the dielectric function from quantitative analysis of the FTIR spectra in Figure 3c.
Figure 5
Figure 5
(a) Band gap determined from the low energy loss region of the reflection electron energy loss spectroscopy (REELS) spectra at primary energy Eo = 1500 eV. (b) Magnetic properties determined by VSM, and (c) reflection loss properties of Fe2O3–carbon for various amounts of carbon (10%, 15%, 20%, and 25% AC).
Figure 6
Figure 6
X-ray photoelectron spectroscopy (XPS) core-level spectra for Fe2O3–carbon with various amounts of carbon (10, 15, 20, and 25% AC). (a) Fe 2p, (b) O 1s, and (c) C 1s.
Figure 7
Figure 7
(a) Absorbance from UV–vis spectra and (b) degradation ability determined from the equation formula image. The kinetic curve of the photocatalytic degradations (c) by formula image and (d) formula image for Fe2O3–carbon for various amounts of carbon (10, 15, 20, and 25% AC).
Figure 8
Figure 8
Relation between the structural (D), magnetic (Hc), and optical properties (Δ and band gap) and the ability to attenuate the electromagnetic wave (RL) and the degradation performance (Deg.).
See this image and copyright information in PMC

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