Integration of WO3-Doped MoO3 with ZnO Photocatalyst for the Removal of 2-Nitrophenol in Natural Sunlight Illumination

Abstract

Environmental contamination has become the most pressing issue in recent years. The value of clean water to mankind has sparked interest in heterogeneous photocatalysis. In this study, a novel photocatalyst has been synthesized by integrating WO3-doped MoO3 (WDM) and ZnO through composite formation. The composite nature of the synthesized photocatalyst was confirmed due to the presence of hexagonal ZnO and orthorhombic WDM phases in XRD pattern and scanning electron micrographs. Solid-state absorption spectra and a bandgap analysis showed that WDM-spectral ZnO’s response was better than that of pure ZnO. PL and EIS unveiled the effective role of WDM in suppressing the e−–h+ recombination process and charge-transfer resistance, respectively, in ZnO. The photocatalytic studies showed that WDM-ZnO was able to remove ~90% of 30 ppm 2-nitrophenol (2-NP) with a rate of 1.1 × 10−2 min−1, whereas ~65% 2-NP was removed by ZnO (6.1 × 10−3 min−1 rate) under the exposure of natural sunlight (800 × 102 ± 100 lx). Moreover, ~52% higher total organic carbon (TOC) removal was observed by WDM-ZnO as compared to ZnO. The photocatalytic removal of 2-NP by the produced photocatalysts followed the Langmuir–Hinshelwood kinetic model, as shown by the kinetic studies. The reactive oxygen species (ROS)-trapping established that the photocatalytic removal mechanism of 2-NP over WDM-ZnO in sunlight illumination was mainly triggered by the superoxide anion (O2•−) radical, however, the minor role of hydroxyl (•OH) radicals cannot be completely ignored.

Characterization and Comparison of WO3/WO3-MoO3 and TiO2/TiO2-ZnO Nanostructures for Photoelectrocatalytic Degradation of the Pesticide Imazalil

“…Diffraction peaks corresponding with the crystalline planes of the monoclinic phase of WO 3 (0 2 0), (2 0 0), (1 1 2), (0 2 2), (2 2 0), and (2 1 1) are observed at 23.5°, 24.3°, 28.8°, 33.4°, 48.0°, and 50.5° [ 33 , 34 , 35 , 36 ]. In addition, peaks from the orthorhombic MoO 3 phase are also appreciated: 23.1° and 40.0°, corresponding to the planes (1 1 0) and (0 6 0), respectively [ 25 , 37 , 38 ].…”

Enhancing Methyl Orange Degradation with Laser-Generated ZnO and Ce-Doped ZnO Nanoparticles

“…The system has electrons in the CB (−0.56 eV) for O 2 • − generation and holes in the V B (+3.14 eV) of ZnO for •OH generation. Furthermore, the valence band maximal positions of ZnO were 3.14 eV [43,44]. On the other hand, for Ce-doped ZnO NPs, a distinct mechanism comes into play.…”

“…These photogenerated holes have the ability to oxidize water molecules within the photocatalytic system or hydroxyl ions adsorbed on the catalyst's surface, resulting in the formation of hydroxyl free radicals (•OH). Simultaneously, the photogenerated electrons interact with adsorbed oxygen molecules to produce superoxide anion radicals [43].…”