Development of Binder Free Interconnected 3D Flower of NiZn2O4 as an Advanced Electrode Materials for Supercapacitor Applications

The design and development of electrode materials for energy-storage applications is an area of prime focus around the globe because of the shortage of natural resources. In this study, we developed a method for preparing a novel three-dimensional binder-free pseudocapacitive NiZn2O4 active material, which was grown directly over nickel foam (NiZn2O4@3D-NF), using a simple one-step hydrothermal process. The material was characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy techniques were employed to evaluate the pseudocapacitive performance of the NiZn2O4 active material in a three-electrode assembly cell. The prepared NiZn2O4@3D-NF electrode exhibited an excellent specific capacitance, of 1706.25 F/g, compared to that of the NiO@3D-NF (1050 F/g) electrode because it has the bimetallic characteristics of both zinc and nickel. The NiZn2O4@3D-NF electrode showed better cyclic stability (87.5% retention) compared to the NiO@3D-NF electrode (80% retention) after 5000 cycles at a fixed current density, which also supports the durability of the NiZn2O4@3D-NF electrode. The characteristics of NiZn2O4@3D-NF include corrosion resistance, high conductivity, an abundance of active sites for electrochemical reaction, a high surface area, and synergism between the bimetallic oxides, which make it a suitable candidate for potential application in the field of energy storage

Polythiophene nanocomposites for photodegradation applications: Past, present and future

Polythiophene (PTh) has been the subject of considerable interest because of its good environmental stability, unique redox electrical behavior, stability in doped or neutral states, ease of synthesis, and wide range of applications in many fields. Apart from its applications in the electrical or electronic field, PTh has shown promising applications in photocatalytic degradation. The fabrication of a catalyst, metal oxides with PTh, extends the absorption range of the modified composite system, thereby enhancing the photocatalytic activity under UV or visible light irradiation. Substituted PTh, such as alkyl substitution, modifies the electronic properties of the polymer, thereby enlarging the potential for industrial applications. PTh or substituted PTh when combined with metal, metal oxide or a combination of both, can exhibit tailorable photocatalytic properties. This review focuses on the chemistry of the band gap engineering of PTh or PTh based systems and the mechanism of photocatalytic degradation. The major developments in the field of UV and visible light-assisted photocatalysis are discussed in terms of the parameters that affect the photocatalytic efficiency. On the other hand, some challenges still needs to be investigated experimentally, which are mentioned as the scope for future studies. For simplicity, the review has been classified under a major subheading depending on the type of composite system used for photocatalysis

Large spin-dependent tunneling magnetoresistance in Fe3O4/PET heterostructures developed at room temperature: A promising candidate for flexible and wearable spintronics

Half-metallic nanocrystalline magnetite (Fe3O4) thin films, with different thicknesses were developed on polyethylene-terephthalate (PET) substrates, by reactive sputtering at room temperature. Fe3O4 film (200-nm thick)/PET heterostructures possess superior electrical and magnetic characteristics, with a Verwey transition temperature (Tv) of ~122 K and a saturation magnetization (Ms) ~ 361 emu/cm3. Furthermore, the antiferromagnetic (AFM)-coupled antiphase boundaries (APBs) controlled the transport properties of the Fe3O4 thin films, due to the tunneling of spin-polarized electrons through the films. Very-high magnetoresistance (MR) value (−8.9%) were observed for HFilm plane, constructed from Fe3O4 (200-nm thick)/PET when H values were below 60 kOe at 300 K. In addition, flexibility tests, to examine resistivity, M-H and MR, were performed using with 90° and 45° bent angles and cyclability experiments were implemented to validate the reproducibility of these characteristics. These outcomes demonstrated that Fe3O4/PET heterostructures may represent a promising candidate for flexible/wearable spintronics

Progress in Fe3O4-centered spintronic systems: development, architecture, and features

Spintronics, or spin-based electronics, is a rapidly growing multidisciplinary research area in the development of physical mechanisms based on the spin as well as the charge of an electron. The initial phase of spintronics had a significant influence on the information storage technology sector after the invention of giant magnetoresistance (GMR) in magnetic multilayers of two different transition metals. In contrast, the next phase of spintronics relies on amalgamating magnetic and semiconducting components to improve electronic gadgets. Spin effects have long been studied in traditional ferromagnetic substances, but research into spin production, relaxation, and spin–orbit relationships in non-magnetic materials has only recently started. The introduction of hybrid spintronic materials and design has created exciting possibilities. This article discusses the recent advancements in the research and development of a variety of Fe3O4-based hybrid spintronic structures based on the half-metallicity and other remarkable capabilities of magnetite (Fe3O4), especially thin-film architectures on traditional, two-dimensional (2D) carbon materials, flexible polymer substrates, and nanocomposites. Half-metallic hybrid systems exhibit strong spin polarity at Fermi energies, whereas 2D structures have exceptional electronic band structures such as Dirac cones and the valley degree of freedom. Massive improvements have been attained in synthesizing and unleashing modern patterns and features from atomic configurations and the heterointerfaces of the epitaxially developed hybrid systems for spintronics. Spin-insertion and recognition, including 2D carbon materials such as graphene and transitional-metal dichalcogenides (TMDs), which are potentially leafy due either to the long spin-life, or the strong spin–orbit coupling, are the most recent areas of increased research interest. Semiconducting matter in groups-IV, III-V, and II-VI, and their nanoscale forms, is another area of great interest. In contrast, using the self-template (ST) approach combined with epitaxial growth of Fe3O4 thin films through any of the physical vapor deposition (PVD) techniques on flexible polymer substrates have triggered the field of wearable and implantable spintronics

Effect of Washing on the Electrochemical Performance of a Three-Dimensional Current Collector for Energy Storage Applications

The development of efficient materials for energy storage applications has attracted considerable attention, especially for supercapacitors and batteries that are the most promising and important power sources in everyday life. For this purpose, a suitable and efficient current collector must be determined and its behavior with respect to various solvents when it is used as an electrode material for energy storage applications should be understood. In this work, we studied the effect of washing three-dimensional nickel foam using different concentrations of hydrochloric acid and ethanol on the surface characteristics, electrochemical behavior, and storage performance of the foam. Additionally, we observed the different types of acidic treatments that improved the electrochemical and storage performances of the three-dimensional nickel foam. The surface characterization results show that acidic conditions with a concentration of 3M changes the surface morphology from a flat/hill-like structure to a nanosheet/nanoflake-like structure without any further treatment. This structure provides a nano-channel and a large number of surface charges during the electrochemical reaction. The results of this study show that pretreatment of 3D-NF is highly important and recommended. The present work also contributes to the knowledgebase on pretreatment of 3D-NF and its optimization

Inside–outside OH– incursion involved in the fabrication of hierarchical nanoflake assembled three-dimensional flower-like α-Co(OH)2 for use in high-performance aqueous symmetric supercapacitor applications

Introduction: The energy industry has been challenged by the current high population and high energy consumption, forcing the development of effective and efficient supercapacitor devices. The crucial issues until now have been high production cost, deprived cyclic stability, and squat energy density. To resolve these problems, various approaches have been taken, such as the development of long-life electrode materials with high capacity, rapid charging, and slow discharging to overcome poor life cycle stability. Objectives: In the present work we focus on fabricating cost-effective unique-morphology, high-surface-area alpha-Co(OH)2 for application in an aqueous-electrolyte symmetric supercapacitor. Methods: In this study, hierarchical nanoflakes assembled in three-dimensional (3D) flower-shaped cobalt hydroxide (HN-3DF-α-Co(OH)2) electrode were synthesized using the solvothermal method with sodium dodecylbenzene sulfonate (SDBS) and methanol as solvents. Spectroscopic and microscopic techniques were used to characterize fabricated HN-3DF-Co(OH)2, which revealed that the materials electrode exhibited the alpha phase with a hierarchical flower-like structure. A half-cell electrochemical assembly (three-electrode assemble cell) and symmetric full cell (two-electrode assemble cell) were examined in an aqueous electrolyte. Results: In three-electrode assembly cells, HN-3DF-α-Co(OH)2 exhibited 719.5 Fg−1 specific capacitance (Csp) at 1 Ag−1 with excellent cyclic retention stability of approximately 88% after 3000 cycles. In two-electrode symmetric supercapacitive systems, HN-3DF-α-Co(OH)2 achieved a maximum Csp of 70.3 Fg−1 at 0.4 Ag−1 with the highest energy density of approximately 6.25 Wh/kg at a power density of 328.94 W/kg. The fabricated two-electrode assembly cell with the HN-3DF-α-Co(OH)2 electrode retained cyclic stability of approximately 85% after 5000 repeated charge and discharge cycles. Conclusion: Solvothermally-synthesized, optimized HN-3DF-α-Co(OH)2 showed outstanding electrochemical performance results in three- and two-electrode systems. This unique aqueous symmetric supercapacitor can be used to design cost-effective symmetric capacitors based on metal hydroxide

Development of Binder Free Interconnected 3D Flower of NiZn₂O₄ as an Advanced Electrode Materials for Supercapacitor Applications

The design and development of electrode materials for energy-storage applications is an area of prime focus around the globe because of the shortage of natural resources. In this study, we developed a method for preparing a novel three-dimensional binder-free pseudocapacitive NiZn2O4 active material, which was grown directly over nickel foam (NiZn2O4@3D-NF), using a simple one-step hydrothermal process. The material was characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy techniques were employed to evaluate the pseudocapacitive performance of the NiZn2O4 active material in a three-electrode assembly cell. The prepared NiZn2O4@3D-NF electrode exhibited an excellent specific capacitance, of 1706.25 F/g, compared to that of the NiO@3D-NF (1050 F/g) electrode because it has the bimetallic characteristics of both zinc and nickel. The NiZn2O4@3D-NF electrode showed better cyclic stability (87.5% retention) compared to the NiO@3D-NF electrode (80% retention) after 5000 cycles at a fixed current density, which also supports the durability of the NiZn2O4@3D-NF electrode. The characteristics of NiZn2O4@3D-NF include corrosion resistance, high conductivity, an abundance of active sites for electrochemical reaction, a high surface area, and synergism between the bimetallic oxides, which make it a suitable candidate for potential application in the field of energy storage

Magnetite thin films grown on different flexible polymer substrates at room temperature: Role of antiphase boundaries in electrical and magnetic properties

Currently, there is an enormous need for flexible electronic devices given their astonishing competencies. In this view, we investigated the structural, electrical, and magnetic characterstics of magnetite (Fe3O4) thin films with a thickness of 100 nm prepared using a reactive RF sputtering technique at 300 K on polycarbonate (PC), polymethyl methacrylate (PMMA), and polythene terephthalate (PET) flexible substrates. The structural properties showed that the films grown on PC, PMMA, and PET substrates exhibited the pure form of Fe3O4 nanostructures by flowing oxygen with a flow rate of 3.5 sccm. The Verwey transition temperatures (Tv) of -123 K, -124 K, and -126 K; saturation magnetization (Ms) values of-220 emu/cm(3y),-235 emu/cm(3), and -261 emu/cm(3); and magnetoresistance (MR) values of-7.1%,-7.3%, and-7.8% under the HIIFilm plane below 60 kOe at 300 K for 100-nm-thick Fe3O4 film on PC, PMMA, and PET substrates respectively were observed. These remarkable results were interpreted and the effect of antiferromagnetically (AFM) coupled antiphase boundaries (APBs) was explained, which suggested that Fe3O4/PET heterostructure can be a most promising component for flexible spintronics

Linear /nonlinear optical susceptibility spectroscopic constants of polyaniline@graphene oxide nanocomposite thin films

Graphene based conducting polymer composites are emerging contenders for newer optoelectronics devices like solar cells and linear / nonlinear optical devices. Beside these advanced applications, characterization approaches to analyze their liner/nonlinear optical constants, surface chemical state and structural analysis in thin film states are much needed. Herein, we reported a facile approach for the fabrication of graphene oxide (GO) and polyaniline (PANI) nano composites (PANI/GO) thin films using spin coating. Thereafter, the liner/nonlinear optical constants including first and third order nonlinear optical susceptibility were calculated using UV–vis (UV–vis) near infra-red absorption spectroscopic technique which will be an alternative to Z-scan approach and is poorly explored till now for such composites. Moreover, the increase or decrease in elemental bonding or interactions between C–C, C–O, C–O–C, C–N and percentage occurrence of C–OH, O–C[dbnd]O, –NH 2 , –N + H=, and –N + H 2 – functionalities in PANI/GO composites were concisely explored using X-ray photoelectron spectroscopy (XPS). Addition to proving the amorphous nature of PANI/GO composites in their X-ray diffraction studies, an increase in intensity of GO peak was explored due to an increase in elemental interactions among the GO and PANI. The reduction in band gap (3.27 to 2.66 eV) and diameter of Sp 2 carbon (19.62 to 15.96 nm) of PANI/GO thin films was observed with an increase in the GO concentration. The first order nonlinear optical susceptibility (X (1) ) is influenced by π-π* and n- π* interaction. The third order nonlinear optical susceptibility (X (3) ) was found in the range of 10 −10 to 10 -7 esu which can be further, optimized by changing the ratio of GO and PANI

Biogenic Synthesis, Photocatalytic, and Photoelectrochemical Performance of Ag–ZnO Nanocomposite

The development of coupled photoactive materials (metal/semiconductor) has resulted in significant advancements in heterogeneous visible light photocatalysis. This work reports the novel biogenic synthesis of visible light active <i>Ag</i>–ZnO nanocomposite for photocatalysis and photoelectrode using an electrochemically active biofilm (EAB). The results showed that the EAB functioned as a biogenic reducing tool for the reduction of Ag⁺, thereby eliminating the need for conventional reducing agents. The as-prepared <i>Ag</i>–ZnO nanocomposite was characterized by X-ray diffraction, transmission electron microscopy, diffuse reflectance spectroscopy, photoluminescence spectroscopy, and X-ray photoelectron spectroscopy. The photocatalytic experiments showed that the <i>Ag</i>–ZnO nanocomposite possessed excellent visible light photocatalytic activity for the degradation of methyl orange, methylene blue, and 4-nitrophenol. Electrochemical impedance spectroscopy and linear scan voltammetry under dark and visible light irradiation confirmed the enhanced visible light activity of the <i>Ag</i>–ZnO as photocatalyst and photoelectrode. These results suggest that Ag nanoparticles induced visible light photocatalytic degradation and enhanced the visible light activity of the photoelectrodes by minimizing the recombination of photogenerated electrons and holes, thereby extending the response of pure ZnO to visible light