Electrospinning Equipment: Electrospun TiO 2 ​ /NiO Nanofibers for Acetaminophen Degradation

I. Background

With the rapid growth of industrialization and a sharp increase in pharmaceutical consumption, pharmaceutical residues in water bodies, such as acetaminophen, have become a global environmental threat. Traditional adsorption methods face difficulties in regeneration, while photocatalytic technology has attracted much attention due to its green and efficient characteristics. Titanium dioxide (TiO2) is a classic photocatalyst, but its wide bandgap (only absorbing ultraviolet light) and rapid electron - hole recombination limit its practical applications. Therefore, researchers have proposed optimizing photocatalytic performance by constructing heterojunctions (such as the combination of p - type NiO and n - type TiO2).

II. Abstract

In this study, NiO−TiO2 nanofibers were successfully prepared for the first time via the sol - gel method combined with electrospinning technology using an electrospinning machine, and their structures were optimized by calcination at 500 °C. Experiments showed that 5 wt% NiO−TiO2 nanofibers achieved a degradation rate of 98.8% for ACT within 4 hours under visible light, nearly doubling that of pure TiO2. Combining with DFT calculations, the mechanism of NiO promoting charge separation was revealed, and the material stability was verified through cycling experiments. This achievement provides new ideas for the design of customized photocatalysts.

III. Core Content

(1) Preparation of Composite Nanofibers

A variety of chemical reagents were selected in the research. Different contents of NiO were dispersed in ethanol, while titanium tetraisopropoxide was dissolved in a mixed solution of acetic acid and ethanol, and polyvinylpyrrolidone was added. The obtained solution was then processed through an electrospinning device and then calcined at 500 °C to obtain NiO−TiO2 composite nanofibers with different NiO contents, such as TN1 (1 wt% NiO−TiO2), TN3 (3 wt% NiO−TiO2), and TN5 (5 wt% NiO−TiO2). This electrospinning method directly doped NiO into TiO2 nanofibers, avoiding the complex steps of using precursors in traditional methods and achieving efficient composite of NiO and TiO2.

(2) Structural and Morphological Characterization

The surface morphology and internal structure of the nanofibers were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that all samples maintained the nanofiber morphology, and the fiber diameter slightly increased with the increase of NiO content (Figure 1). X - ray diffraction (XRD) analysis indicated that the introduction of NiO promoted the phase transition of TiO2 from anatase to rutile, suggesting that the doping of NiO had a significant impact on the crystal structure of TiO2​.

Figure 1. SEM Images of TN1, TN3, and TN5 Samples

(3) Photocatalytic Performance Test

Using a visible light halogen lamp as the light source to simulate natural lighting conditions, acetaminophen degradation experiments were carried out on the prepared samples. The results showed that the addition of NiO significantly improved the photocatalytic efficiency of the composites, and the TN5 sample had the highest degradation efficiency (see Figure 2). Within 4 hours, the degradation efficiency of acetaminophen by the TN5 sample reached 98.8% (see Figure 2a).

Figure 2. (a) Degradation of ACT with Different NiO Concentrations on TiO₂, and (b) Corresponding Photocatalytic Kinetics

(4) Mechanism Analysis

The electronic structure and charge transfer mechanism of the NiO−TiO2 composite were studied by density functional theory (DFT) calculations. The calculation results showed that the introduction of NiO significantly changed the electronic structure of TiO2, promoting the separation of photogenerated carriers and visible light absorption (Figure 3). In addition, radical quenching experiments verified the crucial roles of superoxide radicals and holes in the degradation process.

Figure 3. Simplified Model of the NiO-TiO₂ Catalyst for ACT Degradation under Visible Light

After 5 cycling experiments, the photocatalytic efficiency of TN5 decreased by only 19%, and its initial activity could be completely restored by thermal regeneration treatment at 500 °C (Figure 4). This indicates that the NiO−TiO2 composite nanofibers have excellent stability and reusability, showing great potential for practical applications.

Figure 4. Cycling Experiment Results of the TN5 Sample

IV. Research Innovation

In this study, NiO−TiO2 nanofibers were successfully prepared by an innovative electrospinning method using an electrospinning machine, and efficient degradation of acetaminophen was achieved under visible light. The introduction of NiO significantly enhanced the photocatalytic performance of TiO2, especially the 5 wt% NiO - doped TiO2 nanofibers (TN5) exhibited excellent degradation efficiency and stability. In addition, DFT calculations revealed the charge transfer mechanism in theNiO−TiO2 composite, providing a theoretical basis for optimizing photocatalytic efficiency. This study not only provides a new high - efficiency photocatalytic material for water pollution treatment but also offers important references for the design of novel composite photocatalysts.

Electrospinning Nanofibers Article Source:

https://doi.org/10.1016/j.colsurfa.2024.136077