Fabrication of ZnO/Au@Cu2O heterojunction towards deeply oxidative photodegradation of organic dyes

Photocatalytic degradation of cetirizine hydrochloride using polypyrrole decorated zinc ferrite nanohybrids under visible light irradiation

The present work reports photocatalytic degradation of cetirizine hydrochloride (CTZ-HCl) utilizing polypyrrole (PPy) nanohybrids with ZnFe2O4 (ZnFe) nanoparticles. The synthesized materials were characterized using UV-visible spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), photoluminescence (PL) spectroscopy, BET, and scanning electron microscopy (SEM) techniques. UV diffuse reflectance studies (UV-DRS) revealed that the band gap was found to decrease with increase in the loading of PPy and Kubelka-Munk plots confirmed the bandgap values to be 2.14 eV for ZnFe, 1.94 eV for 1% PPy/ZnFe, 1.66 eV for 3% PPy/ZnFe, and 1.38 eV for 5% PPy/ZnFe. The photocatalytic performance against CTZ-HCl degradation was performed under visible light irradiation for 60 min. The effect of catalyst dosage and the effect of drug concentration were investigated to confirm degradation behavior of the PPy/ZnFe photocatalysts. The degradation followed the pseudo-first-order kinetics model. Maximum photocatalytic degradation was observed to be 98% within 60 min using 5% PPy/ZnFe as the photocatalyst. The recyclability tests revealed that the 5% PPy/ZnFe photocatalyst was reusable up to 4 cycles. Radical scavenging studies confirmed the generation of ●OH radicals that were responsible for the drug degradation. The degraded fragments were analyzed using LCMS technique and the tentative mechanism of degradation was proposed.

The prospect of CuxO-based catalysts in photocatalysis: From pollutant degradation, CO2 reduction, and H2 production to N2 fixation

The topic of photocatalysis and CuxO-based materials has been intertwined for quite a long time. Its relatively high abundance in the earth's crust makes it an important target for researchers around the globe. One of the properties exploited by researchers is its ability to exist in different oxidation states (Cu0, Cu+, Cu2+, and Cu3+) and its implications on photocatalytic efficiency improvement. Recently, they have been extensively used as photocatalytic materials for dye and pollutant degradation. However, it has almost reached saturation levels, therefore, currently, they are being mostly utilized for CO2 reduction and H2 evolution. Hence, this review will discuss the evolution (in application) of CuxO-based photocatalysts, relating to their past, present, and future. Moreover, photocatalytic efficiency improvement strategies such as doping, heterojunction formation, and carbonaceous construction with other materials will also be touched upon. Finally, the prospect of Cu2O-based photocatalysts will be discussed in the field of photocatalytic N2 fixation to ammonia. The significance of N2 chemisorption on photocatalysts to maximize ammonia production will also be given importance.

In Situ Polymerization of Antibacterial Modification Polyamide 66 with Au@Cu2O-ZnO Ternary Heterojunction

In situ polymerization has proven to be an effective route through which to introduce function materials into polyamide materials. In this work, a nano-heterojunction material was evenly dispersed in PA66 via in situ polymerization methods to yield the antimicrobial PA66. The composites showed excellent antibacterial activity against Staphylococcus aureus and Escherichia coli, with strong mechanical properties. Fourier transform infrared spectroscopy (FTIR) showed that metal ions reacted with oxygen-containing functional groups. In addition, the shift of oxygen peaks in XPS spectra confirmed the occurrence of a complexation reaction. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) confirmed the effect of nano-heterojunction, which induced crystallization. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed uniform dispersion of heterojunctions in PA66. Tensile testing revealed decreased toughness with higher loadings. The nanocomposite polyamide material has good processing properties which can be processed into thin films, molds, and wires without changing the morphology, and can be widely used in a variety of fields.

Immobilization of photocatalytic materials for (waste)water treatment using 3D printing technology - advances and challenges

Photocatalysis has been considered a promising technology for the elimination of a wide range of pollutants in water. Various types of photocatalysts (i.e., homojunction, heterojunction, dual Z-scheme photocatalyst) have been developed in recent years to address the drawbacks of conventional photocatalysts, such as the large energy band gap and rapid recombination rate of photogenerated electrons and holes. However, there are still challenges in the design of photocatalytic reactors that limit their wider application for real (waste)water treatment, such as difficulties in their recovery and reuse from treated (waste)waters. 3D printing technologies have been introduced very recently for the immobilization of materials in novel photocatalytic reactor designs. The present review aims to summarize and discuss the advances and challenges in the application of various 3D printing technologies (i.e., stereolithography, inkjet printing, and direct ink writing) for the fabrication of stable photocatalytic materials for (waste)water treatment purposes. Furthermore, the limitations in the implementation of these technologies to design future generations of photocatalytic reactors have been critically discussed, and recommendations for future studies have been presented.

Co3O4 Nanopetals Grown on the Porous CuO Network for the Photocatalytic Degradation

Designing a novel photocatalytic composite for the efficient degradation of organic dyes remains a serious challenge. Herein, the multi-layered Co₃O₄@NP-CuO photocatalyst with unique features, i.e., the self-supporting, hierarchical porous network as well as the construction of heterojunction between Co₃O₄ and CuO, are synthesized by dealloying-electrodeposition and subsequent thermal treatment techniques. It is found that the interwoven ultrathin Co₃O₄ nanopetals evenly grow on the nanoporous CuO network (Co₃O₄@NP-CuO). The three-dimensional (3D) hierarchical porous structure for the catalyst provides more surface area to act as active sites and facilitates the absorption of visible light in the photodegradation reaction. Compared with the commercial CuO and Co₃O₄ powders, the newly designed Co₃O₄@NP-CuO composite exhibits superior photodegradation performance for RhB. The enhanced performance is mainly due to the construction of heterojunction of Co₃O₄/CuO, greatly promoting the efficient carrier separation for photocatalysis. Furthermore, the possible photocatalytic mechanism is analyzed in detail. This work provides a promising strategy for the fabrication of a new controllable heterojunction to improve photocatalytic activity.

Decorating of Ag and CuO on ZnO Nanowires by Plasma Electrolyte Oxidation Method for Enhanced Photocatalytic Efficiency

In this work, photocatalytic performance is divulged in the ternary CuO-Ag-ZnO nanowire synthesized via a two-step approach. The decoration of Ag and CuO nanostructures onto the surface of ZnO nanowires was simply carried out by using the plasma electrolytic oxidation method in a short time. The structure, size, morphology, and optical properties of as-prepared samples were characterized by X-ray diffraction, field-emission scanning electron microscopy, and spectrophotometry measurements. The diameters of Ag nanoparticles and ZnO nanoflowers are in the range of 5–20 nm and 20–60 nm, respectively. Within the first 15 min, methyl orange was decolorized 96.3 and 82.8% in the CuO-Ag-ZnO and Ag-ZnO, respectively, and there is only about 46.7% of that decomposed in pure ZnO. The CuO-Ag-ZnO shows a higher rate constant k = 0.2007 min−1 and a lower half-life time t = 6.1 min compared to Ag-ZnO and bare ZnO nanowires. The photo-reusability of the ternary nanostructures was estimated to be much outweighed compared to ZnO nanowires. Interestingly, the synergic incorporation between noble metal–semiconductor or semiconductor–semiconductor in the interfaces of Ag-CuO, Ag-ZnO, and CuO-ZnO expands the visible light absorption range and eliminates the photogenerated electron–hole recombination, resulting in a superior visible-light-driven photocatalyst.

Electrochemically enhanced adsorption of organic dyes from aqueous using a freestanding metal-organic frameworks/cellulose-derived porous monolithic carbon foam

Monolithic carbon foams are promising materials for adsorption due to the easy recyclability and without secondary-pollution. However, poor adsorption efficiency for organic pollutants limits its practical application. Hence, this work proposed a novel monolithic porous carbon foam by a facile carbonization approach as freestanding electrodes to remove the organic dyes. The prepared carbon foam derived from waste cigarette filters and zeolitic-imidazolate frameworks-8 with well-developed pores, and the calculated surface area is 1457 m²·g^-1, and exhibited an outstanding removal efficiency for methylene blue in aqueous. The maximum adsorption capacity for methylene blue can reach up to 1846.7 mg·g^-1 under the applied voltage of -1.2 V. Importantly, as-prepared carbon foams possessed excellent stability, and the removal efficiency can remain above 85% after 5 cycles. Thus, obtained porous carbon foams in this paper as a free standing electrode is expected to be promising materials of adsorbent besides supercapacitors.