Electrospinning preparation of NiO/ZnO composite nanofibers for photodegradation of binary mixture of rhodamine B and methylene blue in aqueous solution: Central composite optimization

Abstract

One-dimensional nanofiber of p-type NiO/n-type ZnO heterojunctions with various molar ratios of Ni to Zn at different calcination temperatures were successfully synthesized using the electrospinning method, and they were fully characterized. The photocatalysts thus obtained were applied in aqueous solutions for rhodamine B (RDB) and methylene blue (MB) degradation. The p-n heterojunctions built among the cubic structure NiO and hexagonal structure ZnO in the composite nanofiber are responsible for generation of electrons and holes and subsequently superoxide and hydroxyl radical production by carriers which lead to degradation of the dyes in solution. The composite nanofibers (ZnNi1) calcined at 550°C for 3 h showed the highest photocatalytic activity for degradation of the dyes in aqueous solution. The optimum values were found to be 180 min, 7.0, 1 g l −1 and 3.0 and 3.0 mg l −1 for irradiation time, pH, photocatalyst dosage and initial concentration of RDB and MB, respectively. For these optimum conditions, the photocatalytic degradation of RDB and MB was found to be 99.37 and 98.44%, respectively. The maximum photodegradation of RDB and MB using ZnNi1 was 59.41 and 65.43%, respectively. First-order kinetics based on the Langmuir-Hinshelwood model successfully fitted the experimental data.

Thermal properties of electrospun polyvinylpyrrolidone/titanium tetraisopropoxide composite nanofibers

“…Numerous metal oxide nanofibers (e.g., ZnO, TiO 2 , MnO 2 , WO 3 , V 2 O 5 , NiO, SnO 2 , Fe 2 O 3 ) [15] or composites (e.g., NiO/ZnO [16], SnO 2 /TiO 2 [17], carbon/MnO 2 [18]) containing different metal oxides can be easily prepared by electrospinning. Out of these oxides, TiO 2 nanofibers are the most widely researched.…”

Photocatalytic Performance of NiO/NiTiO3 Composite Nanofiber Films

“…This phenomenon can encourage in situ absorption of oxygen to generate superoxide radicals, O2 − . [37][38][39] At the same time, Rhodamine B is decomposed due to the hole (h + ) in NiO and NiTiO3 generated by photo illumination. Since the potential of the valence band of NiTiO3 is higher than the potential of H2O/•OH (2.38 eV vs. NHE), both superoxide O2 − radicals and photogenerated holes play a role in photocatalytic The mechanism of photocatalytic degradation enhancement of the NiO/NiTiO 3 composite is discussed in Figure 9.…”

“…At the p-n heterojunction interface of NiO and NiTiO 3 , the boundary potential of the NiO conduction band (−1.23 eV vs. NHE) is lower than that of NiTiO 3 (0.23 eV vs. NHE) [35,36], resulting in easy transfer of photogenerated electrons from the conduction band of NiO to the conduction band position of NiTiO 3 . This phenomenon can encourage in situ absorption of oxygen to generate superoxide radicals, O 2 − [37][38][39]. At the same time, Rhodamine B is decomposed due to the hole (h + ) in NiO and NiTiO 3 generated by photo illumination.…”

NiO Nanosheets Coupled With CdS Nanorods as 2D/1D Heterojunction for Improved Photocatalytic Hydrogen Evolution

“…Nickel oxide (NiO), as a low-cost and earth-abundant p-type semiconductor, has attracted significant attention in the field of photocatalysis, including photocatalytic degradation (Ahmad et al, 2018;Sabzehmeidani et al, 2018), photocatalytic CO 2 reduction (Chen et al, 2018), and photocatalytic hydrogen evolution (Shi et al, 2019;Lin et al, 2020). However, many previous studies mainly focused on the NiO nanoparticles; the 2D sheet-like NiO nanosheets for photocatalytic application were seldom discussed.…”