Tuning Composition of Electrospun ZnO/CuO Nanofibers: Toward Controllable and Efficient Solar Photocatalytic Degradation of Organic Pollutants

Abstract

ZnO/CuO nanofibers, with different CuO concentrations, were fabricated by one-step electrospinning of the polymer precursor and annealing in air. Scanning electron microscopy (SEM) showed smooth and beadless morphology for the synthesized nanofibers, while X-ray diffraction (XRD) analysis revealed formation of hexagonal and monoclinic crystalline structure phases for ZnO and CuO nanofibers, respectively. X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of CuO on the surface of ZnO nanofibers. For further confirming the formation of chemical bonds, Fourier transform infrared (FT-IR) spectroscopy was employed. The effect of Cu contents in the overall electronic band structure of ZnO was explained by density functional theory (DFT) calculations. Diffuse reflectance spectroscopy (DRS) showed that the ZnO band gap energy reduced with increasing amount of CuO contents due to the presence of the Cu­(3d) energy states above the valence band. Comparing the photocatalytic activity of ZnO/CuO nanofiber samples with different CuO concentrations under similar sunlight irradiation conditions revealed that the ZnO/(0.5 wt %) CuO sample exhibited the highest performance among all samples. This was explained by an effective suppression of electron–hole recombination as verified by both photoluminescence (PL) and photocurrent density measurements. By means of charge carrier scavengers, it was found that holes and hydroxyl radicals are the main surface species for photocatalytic degradation of methylene blue (MB) over the ZnO/(0.5 wt %) CuO nanofiber. Furthermore, the optimized sample demonstrated great activity for the degradation of bisphenol A (BPA) with a rate constant of 3.4 × 10–2 min–1. Finally, a photocatalytic degradation mechanism based on the main reactive oxygen species (ROS) and calculated band positions was proposed.

Morphological Control of Mesoporosity and Nanoparticles within Co3O4–CuO Electrospun Nanofibers: Quantum Confinement and Visible Light Photocatalysis Performance

“…The shakeup satellite peaks located at approximately 940.75, 942.80, and 961.37, 962.41 eV are attributed to the Cu (3d) hole states. 53 These satellite peaks also confirm the Cu(II) bonding state of CuO in the composite Co 3 O 4 −CuO NFs. 54 The XPS spectrum of Co 2p in Figure 7 shows that the peaks at approximately 780.…”

Quantitative characterization of the long-term charge storage of a ZnO-based nanorod array film through persistent photoconductance

“…The peaks at 932.92 eV and 952.79 eV belong to Cu-2p 3/2 and 2p 1/2 respectively. 20,21 The shakeup satellite peaks typical of Cu 2+ are too weak to be observed. All the Cu(CH 3 COO) 2 -coated ZnO nanorods samples present a similar XPS spectrum of Cu-2p, unambiguously conrming the presence of Cu 2+ .…”

Electrochemically anodized one-dimensional semiconductors: a fruitful platform for solar energy conversion

“…Environmental remediation Non-selective photocatalysis has been extensively explored owing to its great significance to environmental remediation [139], by which contaminants are completely mineralized to less toxic inorganic compounds, such as water, carbon dioxide, and salts. Spatially ordered anodized 1D metal oxides can serve as efficient photocatalysts in non-selective degradation of organic pollutants for environmental amelioration on account of their superior electron mobility, high adsorption capacity and large specific surface area [138,140,141]. For example, as demonstrated by Zheng's group [138], CuWO 4 @Cu 2 O film was prepared on the copper mesh by a one-step anodization method.…”