Synthesis of NiMn2O4/PANI nanosized composite with increased specific capacitance for energy storage applications

Polyaniline (PANI) stands out as a highly promising conducting polymer with potential for advanced utilization in high-performance pseudocapacitors. Therefore, there exists a pressing need to bolster the structural durability of PANI, achievable by developing composite materials that can enhance its viability for supercapacitor applications. In this particular study, a pioneering approach was undertaken to produce a novel NiMn2O4/PANI supercapacitor electrode material. A comprehensive array of analytical techniques was employed to ascertain the structural configuration, morphology, oxidation states of elements, composition, and surface characteristics of the electrode material. The electrochemical evaluation of the NiMn2O4/PANI composite shows a specific capacitance (Cs) of 1530 ± 2 F g-1 at 1 A g-1. Significantly, the composite material displays an outstanding 93.61% retention of its capacity after an extensive 10 000 cycles, signifying remarkable cycling stability, while the 2-electrode configuration reveals a Cs value of 764 F g-1 at 5 mV s-1 and 826 F g-1 at 1 A g-1 with a smaller charge transfer resistance (Rct) value of 0.67 Ω. Chronoamperometric tests showed excellent stability of the fabricated material up to 50 h. This significant advancement bears immense promise for its potential implementation in high-efficiency energy storage systems and heralds a new phase in the development of supercapacitor technology with improved stability and performance metrics.

New Insights on Designing the Next-Generation Materials for Electrochemical Synthesis of Reactive Oxidative Species Towards Efficient and Scalable Water Treatment: A Review and Perspectives

Electrochemical water remediation technologies offer several advantages and flexibility for water treatment and degradation of contaminants. These technologies generate reactive oxidative species (ROS) that degrade pollutants. For the implementation of these technologies at an industrial scale, efficient, scalable, and cost-effective in-situ ROS synthesis is necessary to degrade complex pollutant mixtures, treat large amount of contaminated water, and clean water in a reasonable amount of time and cost. These targets are directly dependent on the materials used to generate the ROS, such as electrodes and catalysts. Here, we review the key design aspects of electrocatalytic materials for efficient in-situ ROS generation. We present a mechanistic understanding of ROS generation, including their reaction pathways, and integrate this with the key design considerations of the materials and the overall electrochemical reactor/cell. This involves tunning the interfacial interactions between the electrolyte and electrode which can enhance the ROS generation rate up to ~ 40% as discussed in this review. We also summarized the current and emerging materials for water remediation cells and created a structured dataset of about 500 electrodes and 130 catalysts used for ROS generation and water treatment. A perspective on accelerating the discovery and designing of the next generation electrocatalytic materials is discussed through the application of integrated experimental and computational workflows. Overall, this article provides a comprehensive review and perspectives on designing and discovering materials for ROS synthesis, which are critical not only for successful implementation of electrochemical water remediation technologies but also for other electrochemical applications.

In-situ hydrogen peroxide formation and persulfate activation over banana peel-derived biochar cathode for electrochemical water treatment in a flow reactor

Electrochemical advanced oxidation processes (EAOPs) are effective for the removal of organic contaminants from groundwater. The choice of an affordable cathode material that can generate reactive oxygen species (ROS) such as hydrogen peroxide (H₂O₂) and hydroxyl radicals (•OH) will increase practicality and cost effectiveness of EAOPs. Carbon enriched biochar (BC), which is derived from pyrolysis of biomass, has emerged as an inexpensive and environmentally-friendly electrocatalyst for removing contaminants from groundwater. In this study, a banana peel-derived biochar (BP-BC) cathode packed in a stainless steel (SS) mesh was used in a continuous flow reactor to degrade the ibuprofen (IBP), as a model contaminant. The BP-BC cathodes generate H₂O₂ via a 2-electron oxygen reduction reaction, initiate the H₂O₂ decomposition to generate •OH, adsorb IBP from contaminated water, and oxidize IBP by formed •OH. Various reaction parameters such as pyrolysis temperature and time, BP mass, current, and flow rate, were optimized to maximize IBP removal. Initial experiments showed that H₂O₂ generation was limited (∼3.4 mg mL^-1), resulting in only ∼ 40% IBP degradation, due to insufficient surface functionalities on the BP-BC surface. The addition of persulfate (PS) into the continuous flow system significantly improves the IBP removal efficiency via PS activation. The in-situ H₂O₂ formation and PS activation over BP-BC cathode results in concurrent generation of •OH and sulfate anion radicals (SO₄^•-, a reactive oxidant), respectively, which collectively achieve ∼ 100% IBP degradation. Further experiments with methanol and tertiary butanol as potential scavengers for •OH and SO₄^•- confirm their combined role in complete IBP degradation.

In-situ Electrochemical Synthesis of H2O2 for p-nitrophenol Degradation Utilizing a Flow-through Three-dimensional Activated Carbon Cathode with Regeneration Capabilities

The growing ubiquity of recalcitrant organic contaminants in the aqueous environment poses risks to effective and efficient water treatment and reuse. A novel three-dimensional (3D) electrochemical flow-through reactor employing activated carbon (AC) encased in a stainless-steel (SS) mesh as a cathode is proposed for the removal and degradation of a model recalcitrant contaminant p-nitrophenol (PNP), a toxic compound that is not easily biodegradable or naturally photolyzed, can accumulate and lead to adverse environmental health outcomes, and is one of the more frequently detected pollutants in the environment. As a stable 3D electrode, granular AC supported by a SS mesh frame as a cathode is hypothesized to 1) electrogenerate H2O2 via a 2-electron oxygen reduction reaction on the AC surface, 2) initiate decomposition of this electrogenerated H2O2 to form hydroxyl radicals on catalytic sites of the AC surface 3) remove PNP molecules from the waste stream via adsorption, and 4) co-locate the PNP contaminant on the carbon surface to allow for oxidation by formed hydroxyl radicals. Additionally, this design is utilized to electrochemically regenerate the AC within the cathode that is significantly saturated with PNP to allow for environmentally friendly and economic reuse of this material. Under flow conditions with optimized parameters, the 3D AC electrode is nearly 20% more effective than traditional adsorption in removing PNP. 30 grams of AC within the 3D electrode can remove 100% of the PNP compound and 92% of TOC under flow. The carbon within the 3D cathode can be electrochemically regenerated in the proposed flow system and design thereby increasing the adsorptive capacity by 60%. Moreover, in combination with continuous electrochemical treatment, the total PNP removal is enhanced by 115% over adsorption. It is anticipated this platform holds great promises to eliminate analogous contaminants as well as mixtures.

Impedance Spectroscopy Analysis of PbSe Nanostructures Deposited by Aerosol Assisted Chemical Vapor Deposition Approach

This research endeavor aimed to synthesize the lead (II) diphenyldiselenophosphinate complex and its use to obtain lead selenide nanostructured depositions and further the impedance spectroscopic analysis of these obtained PbSe nanostructures, to determine their roles in the electronics industry. The aerosol-assisted chemical vapor deposition technique was used to provide lead selenide deposition by decomposition of the complex at different temperatures using the glass substrates. The obtained films were revealed to be a pure cubic phase PbSe, as confirmed by X-ray diffraction analysis. SEM and TEM micrographs demonstrated three-dimensionally grown interlocked or aggregated nanocubes of the obtained PbSe. Characteristic dielectric measurements and the impedance spectroscopy analysis at room temperature were executed to evaluate PbSe properties over the frequency range of 100 Hz-5 MHz. The dielectric constant and dielectric loss gave similar trends, along with altering frequency, which was well explained by the Koops theory and Maxwell-Wagner theory. The effective short-range translational carrier hopping gave rise to an overdue remarkable increase in ac conductivity (σac) on the frequency increase. Fitting of a complex impedance plot was carried out with an equivalent circuit model (Rg Cg) (Rgb Qgb Cgb), which proved that grains, as well as grain boundaries, are responsible for the relaxation processes. The asymmetric depressed semicircle with the center lower to the impedance real axis provided a clear explanation of non-Debye dielectric behavior.

α-Fe2O3-based nanocomposites: synthesis, characterization, and photocatalytic response towards wastewater treatment

Recently, rising distress over ecological pollution owing to water contamination by coloring effluents primarily due to dyes is of growing concern. The development of semiconductor/magnetic oxide-based nanomaterials has verified to be a potent remediation means for water pollution. In the present article, the fabrication of nanocomposites was carried out by the facile hydrothermal method. The ZnO and ZnSe nanoparticles were in situ formed on the α-Fe₂O₃ layer, thereby forming a heterojunction. The prepared α-Fe₂O₃/ZnSe nanocomposite possessed a degradation of 98.9% for a Congo red aqueous solution of 100 ppm. The α-Fe₂O₃/ZnO nanocomposite showed only 26% degradation of 100 ppm dye solution depicting a poor photocatalytic performance. This is attributed to the formation of recombination-enhanced configuration (type-I heterostructure) in the α-Fe₂O₃/ZnO nanocomposite (NC). In contrast, α-Fe₂O₃/ZnSe NC accomplished a higher and enhanced photocatalytic response. The key rationale for elevated photocatalytic response is the establishment of a recombination-free configuration (type-II heterostructure). Thus, α-Fe₂O₃/ZnSe NC known as one of outstanding nanoparticle-nanocomposite photocatalysts was synthesized under mild conditions exclusive of some multifaceted post-treatment, for dye abatement process.

Synthesis and characterization of an α-Fe2O3/ZnTe heterostructure for photocatalytic degradation of Congo red, methyl orange and methylene blue

The leading challenge towards environmental protection is untreated textile dyes. Tailoring photocatalytic materials is one of the sustainable remediation strategies for dye treatment. Hematite (α-Fe2O3), due to its favorable visible light active band gap (i.e. 2.1 eV), has turned out to be a robust material of interest. However, impoverished photocatalytic efficiency of α-Fe2O3 is ascribable to the short life span of the charge carriers. Consequently, the former synthesized heterostructures possess low degradation efficiency. The aim of the proposed endeavor is the synthesis of a novel zinc telluride-modified hematite (α-Fe2O3/ZnTe) heterostructure, its characterization and demonstration of its enhanced photocatalytic response. The promising heterostructure as well as bare photocatalysts were synthesized via a hydrothermal approach. All photocatalysts were characterized by the X-ray diffraction technique (XRD), scanning electron microscopy (SEM), and electron diffraction spectroscopy (EDX). Moreover, the selectivity and activity of the photocatalyst are closely related to the alignment of its band energy levels, which were estimated by UV-Vis diffuse reflectance spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS). Nanomaterials, specifically α-Fe2O3 and α-Fe2O3/ZnTe, were used for the degradation of Congo red (97.9%), methyl orange (84%) and methylene blue (73%) under light irradiation (>200 nm) for 60 min. The results suggested that with the aforementioned optimized fabricated heterostructure, the degradation efficiency was improved in comparison to bare hematite (α-Fe2O3). The key rationale towards such improved photocatalytic response is the establishment of a type-II configuration in the α-Fe2O3/ZnTe heterostructure.

Efficient Photoelectrochemical Water Splitting by Tailoring MoS2/CoTe Heterojunction in a Photoelectrochemical Cell

Solar energy conversion through photoelectrochemical water splitting (PEC) is an upcoming promising technique. MoS2/CoTe heterostructures were successfully prepared and utilized for PEC studies. MoS2 and CoTe were prepared by a hydrothermal method which were then ultrasonicated with wt. % ratios of 1:3, 1:1 and 3:1 to prepare MoS2/CoTe (1:3), MoS2/CoTe (1:1) and MoS2/CoTe (3:1) heterostructure, respectively. The pure materials and heterostructures were characterized by XRD, UV-vis-DRS, SEM, XPS, PL and Raman spectroscopy. Photoelectrochemical measurements were carried out by linear sweep voltammetry and electrochemical impedance spectroscopic measurements. A maximum photocurrent density of 2.791 mA/cm2 was observed for the MoS2/CoTe (1:1) heterojunction which is about 11 times higher than the pristine MoS2. This current density was obtained at an applied bias of 0.62 V vs. Ag/AgCl (1.23 V vs. RHE) under the light intensity of 100 mW/cm2 of AM 1.5G illumination. The enhanced photocurrent density may be attributed to the efficient electron-hole pair separation. The solar to hydrogen conversion efficiency was found to be 0.84% for 1:1 MoS2/CoTe, signifying the efficient formation of the p-n junction. This study offers a novel heterojunction photocatalyst, for PEC water splitting.

Hematite and Magnetite Nanostructures for Green and Sustainable Energy Harnessing and Environmental Pollution Control: A Review

The optoelectrical and magnetic characteristics of naturally existing iron-based nanostructures, especially hematite and magnetite nanoparticles (H-NPs and M-NPs), gained significant research interest in various applications, recently. The main purpose of this Review is to provide an overview of the utilization of H-NPs and M-NPs in various environmental remediation. Iron-based NPs are extensively explored to generate green energy from environmental friendly processes such as water splitting and CO₂ conversion to hydrogen and low molecular weight hydrocarbons, respectively. The latter part of the Review provided a critical overview to use H-NPs and M-NPs for the detection and decontamination of inorganic and organic contaminants to counter the environmental pollution and toxicity challenge, which could ensure environmental sustainability and hygiene. Some of the future perspectives are comprehensively presented in the final portion of the script, optimiztically, and it is supported by some relevant literature surveys to predict the possible routes of H-NPs and M-NPs modifications that could enable researchers to use these NPs in more advanced environmental applications. The literature collection and discussion on the critical assessment of reserving the environmental sustainability challenges provided in this Review will be useful not only for experienced researchers but also for novices in the field.

Visible-light active tin selenide nanostructures: synthesis, characterization and photocatalytic activity

Photocatalytic activity and proposed reaction mechanism of degradation of Methylene Blue dye by SnSe nanostructures.

Preparation of 2D hydroxyl-rich carbon nitride nanosheets for photocatalytic reduction of CO2

The nanosheet exhibits better visible-light photocatalytic activity than bulk g-C₃N₄ due to nanosheet nature and presence of more hydroxyl groups.

Hollow and mesoporous ZnTe microspheres: synthesis and visible-light photocatalytic reduction of carbon dioxide into methane

The morphology of hollow and mesoporous ZnTe microspheres synthesized via a hydrothermal method has been controlled and the detailed formation mechanism has been investigated. These microspheres have used for the photoreduction of CO₂ into CH₄.

Synthesis of a Bi2S3/CeO2 nanocatalyst and its visible light-driven conversion of CO2 into CH3OH and CH4

The Bi₂S₃/CeO₂ nanocatalyst can efficiently photoreduce CO₂ into CH₃OH and CH₄ under visible-light irradiation due to Bi₂S₃ sensitization and semiconductor combination.