ZnFe₂O₄‐Decorated Mesoporous Al₂O₃ Modified MCM‐41: A Solar‐Light‐Active Photocatalyst for the Effective Removal of Phenol and Cr (VI) from Water

Abstract

A series of promising visible light driven ZnFe 2 O 4 modified Al 2 O 3 À MCM-41 nanocomposites were designed by wet impregnation method by loading different wt % (2, 6, 10) of ZnFe 2 O 4 on the surface of mesoporous Al 2 O 3 À MCM-41. All the prepared photocatalysts were analyzed by using X-ray diffractometers (XRD), Scanning electron microscope (SEM), N 2 sorption, Ultra violet-Visible Diffuse reflectance spectroscopy (UV-Vis DRS), Xray photoelectron spectroscopy (XPS), Fourier-transmission infrared spectroscopy (FTIR) and High-resolution transmission electron microscope (HRTEM) techniques to uncover and confirm the formation of phase, morphology and porous structure of the prepared nanocomposites. In the photo-Fenton reaction, the ZnFe 2 O 4 modified Al 2 O 3 À MCM-41 nanocomposites exhibit a significant catalytic activity for the photo-Fenton degradation of phenol (40 min, 99%) via photocatalysis and photocatalytic reduction of Cr (VI) (60 min, 66%) under sunlight with an excellent reusability nature. The high photo-Fenton activity of the composites is mainly attributed to mesoporosity and high surface area of support Al 2 O 3 À MCM-41, proper light harvestation and increased charge transfer efficiency by active species ZnFe 2 O 4 , and suitable band edge potential for hydroxyl radical generation. The photo-Fenton activities were further supported by the high photocurrent (0.29 mA/cm 2 ) generated by the nanocomposite ZnFe 2 O 4 modified Al 2 O 3 À MCM-41. These results open up a new route for ZnFe 2 O 4 modified Al 2 O 3 À MCM-41as an efficient photo-Fenton catalyst for environmental remediation with superior activity and higher stability.

Room‐Temperature Self‐Assembled Preparation of Porous ZnFe2O4/MIL‐100(Fe) Nanocomposites and Their Visible‐Light Derived Photocatalytic Properties

“…As the CB potential of MIL‐100(Fe) is more negative than the O 2 /•O 2 ‐ redox couple (‐0.046 eV), the electrons can be captured by dissolved O 2 molecules to produce superoxide radicals •O 2 ‐ . On the other hand, the VB potential of ZnFe 2 O 4 is less positive than the OH ‐ /•OH redox couple (2.73 eV), indicating that the holes from ZnFe 2 O 4 cannot produce •OH radicals directly . However, except for the oxidation of hydroxyls, •OH radicals can also be produced by protonation of superoxide .…”

Bandgap engineering via boron and sulphur doped carbon modified anatase TiO2: a visible light stimulated photocatalyst for photo-fixation of N2 and TCH degradation

“…So, we can say that the conduction band potential of B-CT is À0.41 eV and the VB is 2.19 eV vs. the NHE scale at pH 6.8 as the E g of B-CT is 2.6 eV. 43 Furthermore, it was observed that in doped systems the E  undergoes a negative shi/smaller slope, suggesting a higher donor density, which can be attributed to the presence of oxygen vacancies/defects (proved via XPS and the Urbach energy) and this will lead to effective separation and transport of charge carriers about the electrode-electrolyte interface. 52 Additionally, as the B-doped carbonised TiO 2 has a higher negative E  value, it will show higher charge conductivity and mobility that ultimately boost the catalytic activity.…”

“…All the calculations were made following our previously reported work. 43 Photoluminescence spectroscopy (PL) analysis…”

“…Also, these highly reducing electrons interact with molecular oxygen and produce a superoxide radical as the CB band position is highly negative (À0.41 eV) compared to the standard redox potential (O 2 /cO 2 À ¼ À0.33 eV vs. NHE). 43,55,56 This favours the production of a high amount of superoxide radicals which then react with TCH and initiate the degradation process. Furthermore, the holes in the VB (2.19 eV) are capable of generating hydroxyl radicals (OH/OHc ¼ 1.99 eV vs. NHE) due to their high reduction potential.…”

Oxidative degradation of p-chlorophenol by the persulfate-doped Fe–Mn bimetallic hydroxide, the parametrical significance, and systematical optimization

“…•OH has a higher potential compared with other common oxidants. Furthermore, •OH can be easily produced by 4 several technologies such as Fenton, ozonation, photocatalysis, electrocatalysis, and photoelectrocatalysis (Das et al 2019, Zhou et al 2019. Nevertheless, the redox potential of •OH is changeable in different pH environments (e.g., +2.7 V in acidity and +1.8 V in neutrality), which explicitly weakened its performance to some extent.…”