High Electrochemical Performance and Enhanced Electrocatalytic Behavior of a Hydrothermally Synthesized Highly Crystalline Heterostructure CeO2@NiO Nanocomposite

Ag-CeO2 Based on Electrochemical Sensor for High-Efficient On-Site Detection of Nitrite in Aquaculture Water and Beverages

Nitrite is one of the most common nitrogenous compounds, which is not only an important indicator of aquaculture water but also widely used as a food additive. Its potential toxicity poses a huge threat to aquatic products and human health. Therefore, it is important to develop a convenient and rapid sensor for the high-efficient onsite detection of nitrite. In this work, a novel electrochemical sensor was developed for the qualitative and quantitative analysis of nitrite. The developed nitrite electrochemical detection system is easily applied in onsite detection. The electrochemical working electrode was constructed based on the combination of Ag-CeO2 and conductive carbon paste (CPE) with excellent electrocatalysis activity and rapid electron transfer ability. By the application of the developed system and under the optimal conditions, the linear range was from 40.0 μM to 500.0 μM, and the detection limit was reduced to 4.3 μM. The recovery was between 92.1% and 108.1%, and the relative standard deviations (RSDs) were 0.49%~9.31%. The sensor exhibited superior reproducibility, high stability sensitivity, and anti-interference ability, confirming its effectiveness for nitrite analysis. Finally, the developed electrochemical sensor was successfully applied to detect nitrite in beverages and aquaculture water samples, indicating that this approach has great potential in onsite food testing and environmental monitoring.

Prospective of Agro-Waste Husks for Biogenic Synthesis of Polymeric-Based CeO2/NiO Nanocomposite Sensor for Determination of Mebeverine Hydrochloride

BACKGROUND

The remarkable properties of nickel oxide (NiO) and cerium oxide (CeO₂) nanostructures have attracted considerable interest in these nanocomposites as potential electroactive materials for sensor construction.

METHODS

The mebeverine hydrochloride (MBHCl) content of commercial formulations was determined in this study using a unique factionalized CeO₂/NiO-nanocomposite-coated membrane sensor.

RESULTS

Mebeverine-phosphotungstate (MB-PT) was prepared by adding phosphotungstic acid to mebeverine hydrochloride and mixing with a polymeric matrix (polyvinyl chloride, PVC) and plasticizing agent o-nitrophenyl octyl ether. The new suggested sensor showed an excellent linear detection range of the selected analyte at 1.0 × 10^-8-1.0 × 10^-2 mol L^-1 with regression equation E_mV = (-29.429 ± 0.2) log [MB] + 347.86. However, the unfunctionalized sensor MB-PT displayed less linearity at 1.0 × 10^-5-1.0 × 10^-2 mol L^-1 drug solution with regression equation E_mV = (-26.603 ± 0.5) log [MB] + 256.81. By considering a number of factors, the applicability and validity of the suggested potentiometric system were improved following the rules of analytical methodological requirements.

CONCLUSION

The created potentiometric technique worked well for determining MB in bulk substance and in medical commercial samples.

Bandgap engineering approach for designing CuO/Mn3O4/CeO2 heterojunction as a novel photocatalyst for AOP-assisted degradation of Malachite green dye

A ternary nanohybrid CuO/Mn₃O₄/CeO₂ was developed in the present work using a co-precipitation-assisted hydrothermal method. The designed photocatalyst's structural, morphology, elemental composition, electronic states of elements, and optical properties were studied using corresponding analytical techniques. Results from PXRD, TEM/HRTEM, XPS, EDAX, and PL showed that the desired nanostructure had formed. Using Tauc's energy band gap plot, it was determined that the nanostructures band gap was ~ 2.44 eV, which showed the band margins of the various moieties, CeO₂, Mn₃O₄, and CuO, had modified. Thus, improved redox conditions led to a substantial decrease in the recombination rate of electron-hole pairs, which was further explained by a PL study in that charge separation plays a key role. Under exposure to visible light irradiation for 60 min, it was revealed that the photocatalyst achieved 98.98% of photodegradation efficiency for malachite green (MG) dye. The process of photodegradation proceeded according to a pseudo-first-order reaction kinetic model with an excellent rate of reaction of 0.07295 min^-1 with R² = 0.99144. The impacts of different reaction variables, inorganic salts, and water matrices were investigated. This research seeks to create a ternary nanohybrid photocatalyst with high photostability, visible spectrum activity, and reusability up to four cycles.

Effect of Pd-Doping Concentrations on the Photocatalytic, Photoelectrochemical, and Photoantibacterial Properties of CeO2

Cerium oxide (CeO2) can exhibit good photocatalytic and photoantibacterial activities. However, its light-harvesting property is rather limited due to its large band gap. In order to boost these properties, doping with metal ions can improve light absorption and charge mobility. In this report, CeO2 and palladium−doped CeO2 (Pd−CeO2) NPs were synthesized via the microwave-assisted synthesis method. The structural, optical, and morphological studies of CeO2 and Pd−CeO2 NPs were carried out using various techniques. Mixed phases of CeO2/Ce2O3 were observed in pure CeO2 (S−CeO2) and Pd−CeO2. However, the Ce2O3 phase gradually disappeared upon doping with a higher percentage of Pd. Almost spherical particles were observed with average sizes between 6 and 13 nm. It was found that the incorporation of Pd reduced the particle size. Moreover, band gap energies of S−CeO2 and Pd−CeO2 NPs were reduced from 2.56 to 2.27 eV, and the PL intensities were also quenched with more Pd doping. The shifts in the conduction band and valence band were found to cause the reduction in the band gap energies of S−CeO2 and Pd−CeO2 NPs. In the case of photocatalytic degradation of methylene blue, photoelectrochemical, and photoantibacterial activities, Pd−CeO2 NPs showed enhanced activities under visible light irradiation. Therefore, Pd−CeO2 NPs have been shown to be a visible-light active material.

Facile Controlled Synthesis of Pd-ZnO Nanostructures for Nitrite Detection

The electrocatalytic characteristics of nanostructures are significantly affected by surface structure. The strict regulation of structural characteristics is highly beneficial for the creation of novel nanocatalysts with enhanced electrocatalytic performance. This work reports a nitrite electrochemical sensor based on novel flower-like Pd-ZnO nanostructures. The Pd-ZnO nanocatalysts were synthesized through a simple hydrothermal method, and their morphology and structure were characterized via field-emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). Their electrocatalytical performance in the nitrite oxidation reaction was studied via cyclic voltammetry (CV) and the amperometric technique. Compared to pure ZnO and Pd nanoparticles, the Pd-ZnO nanostructures exhibited enhanced electrochemical performance in the nitrite oxidation reaction. In order to investigate the relationships between the structures of Pd-ZnO nanocatalysts and the corresponding electrocatalytic performances, different surface morphologies of Pd-ZnO nanocatalysts were fabricated by altering the solution pH. It was found that the flower-like Pd-ZnO nanostructures possessed larger effective surface areas and faster electron transfer rates, resulting in the highest electrocatalytic performance in the nitrite oxidation reaction. The designed nitrite sensor based on flower-like Pd-ZnO displayed a wide concentration linear range of 1 μM-2350 μM, a low detection limit of 0.2 μM (S/N of 3), and high sensitivity of 151.9 μA mM^-1 cm^-2. Furthermore, the proposed sensor exhibited perfect selectivity, excellent reproducibility, and long-time stability, as well as good performance in real sample detection.

Rare Earth-Based Nanomaterials for Supercapacitors: Preparation, Structure Engineering and Application

Supercapacitors (SCs) can effectively alleviate problems such as energy shortage and serious greenhouse effect. The properties of electrode materials directly affect the performance of SCs. Rare earth (RE) is known as "modern industrial vitamins", and their functional materials have been listed as key strategic materials. In the past few years, the number of scientific reports on RE-based nanomaterials for SCs has increased rapidly, confirming that adding RE elements or compounds to the host electrode materials with various nanostructured morphologies can greatly enhance their electrochemical performance. Although RE-based nanomaterials have made rapid progress in SCs, there are very few works providing a comprehensive survey of this field. In view of this, a comprehensive overview of RE-based nanomaterials for SCs is provided here, including the preparation methods, nanostructure engineering, compounds, and composites, along with their capacitance performances. The structure-activity relationships are discussed and highlighted. Meanwhile, the future challenges and perspectives are also pointed out. This Review can not only provide guidance for the further development of SCs but also arouse great interest in RE-based nanomaterials in other research fields such as electrocatalysis, photovoltaic cells, and lithium batteries.

Microwave-assisted hydrothermal synthesis of MoS2-Ag3PO4 nanocomposites as visible light photocatalyst for the degradation of tetracycline hydrochloride

In the modern era, industrialization has facilitated the human life but produced several severe pollutants as well that are hazardous in nature. Thus the degradation of these hazardous material has drawn considerable attention. This study deals with the synthesis of MoS₂/Ag₃PO₄ heterojunction nanocomposite with 1-50% wt. using a microwave-assisted hydrothermal process as well as photocatalytic activity of tetracycline hydrochloride (TCH) degradation has been analysed. The compositional properties of nanocomposite catalysts have been studied through X-ray diffraction, Fourier transform infrared, X-ray photoelectron spectroscopy as well as structural and morphological studies were conducted through scanning electron microscopy, transmission electron microscopy, Brunauer-Emmet-Teller, photoluminescence, N₂ physical adsorption, UV-vis diffuse reflectance spectroscopy. This provides an excellent and efficient mechanism for the remediation of residual organic contaminants under visible light that could be used to decontaminate the atmosphere.

Pseudo-Periodically Coupling NiO Lattice with CeO Lattice in Ultrathin Heteronanowire Arrays for Efficient Water Oxidation

Transition metal oxides (TMOs) have been under the spotlight as promising precatalysts for electrochemical oxygen evolution reaction (OER) in alkaline media. However, the slow and incomplete self-reconstruction from TMOs to (oxy)hydroxides as well as the formed (oxy)hydroxides with unmodified electronic structure gives rise to the inferior OER performance to the noble metal oxide ones. Herein, a unique dual metal oxides lattice coupling strategy is proposed to fabricate carbon cloth-supported ultrathin nanowires arrays, which are composed of pseudo-periodically welded NiO with CeO₂ nanocrystals (NiO/CeO₂ NW@CC). When served as an OER precatalyst in 1.0 m KOH, the NiO/CeO₂ NW@CC shows an ultralow overpotential of 330 mV at 50 mA cm^-2 , along with an impressive cycle durability of more than 3 days even at 50 mA cm^-2 , surpassing CC-supported NiO and commercial IrO₂ catalysts. The combined experimental and theoretical investigations unveil that the atomic coupling of CeO₂ can not only appreciably trigger the generation of oxygen vacancies and expedite phase transformation of NiO into active NiOOH, but also in situ create a chemical bond with the formed NiOOH and enable the electron injection, thus effectively inhibiting the aggregation of the accessible NiOOH nanodomains and optimizing their reaction free energy towards oxygen-containing intermediates.

Silver decorated CeO2 nanoparticles for rapid photocatalytic degradation of textile rose bengal dye

High quality silver (Ag) decorated CeO2 nanoparticles were prepared by a facile one-step chemical method. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), High resolution transmission electron microscopy (HR-TEM), fourier transform infrared spectrometer (FT-IR), electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), UV-Visible absorption (UV-Vis), photoluminescence (PL) and thermogravimetric analysis. The decoration of Ag on CeO2 surface was confirmed by XRD, EPR and HR-TEM analysis. Harmful textile pollutant Rose Bengal dye was degraded under sunlight using the novel Ag decorated CeO2 catalyst. It was found that great enhancement of the degradation efficiency for Ag/CeO2 compared to pure CeO2, it can be ascribed mainly due to decrease in its band gap and charge carrier recombination rate. The Ag/CeO2 sample exhibited an efficient photocatalytic characteristic for degrading RB under visible light irradiation with a high degradation rate of 96% after 3 h. With the help of various characterizations, a possible degradation mechanism has been proposed which shows the effect of generation of oxygen vacancies owing to the decoration of Ag on the CeO2 surface.

Structural, Morphological, and Electrochemical Performance of CeO2/NiO Nanocomposite for Supercapacitor Applications

The composite of ceria has been widely studied as an electrode material for supercapacitors applications due to its high energy density. Herein, we synthesize CeO2/NiO nanocomposite via a hydrothermal route and explore its different aspects using various characterization techniques. The crystal structure is investigated using X-ray diffraction, Fourier transform infrared, and Raman spectroscopy. The formation of nanoflakes which combine to form flower-like morphology is observed from scanning electron microscope images. Selected area scans confirm the presence of all elements in accordance with their stoichiometric amount and thus authenticate the elemental purity. Polycrystalline nature with crystallite size 8–10 nm having truncated octahedron shape is confirmed from tunneling electron microscope images. Using X-ray photoelectron spectroscopy the different oxidation states of Ce and Ni are observed which play the role of active sites in the electrochemical performance of this nanocomposite material. Cyclic Voltammetry(CV) measurements at different scan rates and Galvanic Charge Discharge (GCD) measurements at different current densities are performed to probe the electrochemical response which revealed the potential of CeO2/NiO nanocomposite as an electrode material for energy storage devices.

Defective two-dimensional layered heterometallic phosphonates as highly efficient oxygen evolution electrocatalysts

Two-dimensional metal phosphonates can be used as OER catalysts directly and their catalytic performances can be improved greatly by combining heterometal doping and defect engineering methods.

Gold nanoparticles decorated bimetallic CuNi-based hollow nanoarchitecture for the enhancement of electrochemical sensing performance of nitrite

Gold nanoparticles (AuNPs) decorated bimetallic CuNi-based hollow nanoarchitecture (CNHN) are reported for the first time as a nonenzymatic sensor for the quantification of nitrite in neutral solution . The CNHN was prepared via a convenient calcining routine using the bimetallic CuNi-MOFs as a coprecursor. The unique chemical structure of hollow CNHN with high specific surface area and abundant terminal amino groups effectively avoid the aggregation of AuNPs and facilitate the subsequent adsorption of nitrite. The Au/CNHN exhibited high electrocatalytic activity towards nitrite oxidation due to the synergetic catalytic effect of AuNPs and CNHN. Chronoamperometric detection of nitrite at the Au/CNHN/GCE achieved a lower linear calibration range of 0.05 to 1.15 mM, with an LOD of 0.017 μM compared with previous reports. The proposed method obtained satisfactory recoveries for nitrite determination in practical applications, which was verified by UV-Vis spectrophotometry. The prepared sensor based on Au/CNHN featured favorable selectivity and stability, which provides a promising approach for real sample analysis. Graphical abstract.

A unique core-shell structured ZnO/NiO heterojunction to improve the performance of supercapacitors produced using a chemical bath deposition approach

The integration of metal oxide composite nanostructures has attracted great attention in supercapacitor (SC) applications. Herein, we fabricated a series of metal oxide composite nanostructures, including ZnO nanowires, NiO nanosheets, ZnO/CuO nanowire arrays, ZnO/FeO nanocrystals, ZnO/NiO nanosheets and ZnO/PbO nanotubes, via a simple and cost-effective chemical bath deposition (CBD) method. The electrochemical properties of the produced SCs were examined by performing cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) analysis, and electrochemical impedance spectroscopy (EIS). Of the different metal oxides and metal oxide composites tested, the unique surface morphology of the ZnO/NiO nanosheets most effectively increased the electron transfer rate and electrical conductivity, which resulted in improved energy storage properties. The binder-free ZnO/NiO electrode delivered a high specific capacitance/capacity of 1248 F g-1 (599 mA h g-1) at 8 mA cm-2 and long-term cycling stability over the course of 3000 cycles with a capacity retention of 79%. These results suggested a superiority in performance of the ZnO/NiO nanosheets relative to the nanowires, nanowire arrays, nanocrystals, and nanotubes. Thus, the present work has provided an opportunity to fabricate new metal oxide composite nanostructures with high-performance energy storage devices.