Two-Dimensional Tungsten Oxide/Selenium Nanocomposite Fabricated for Flexible Supercapacitors with Higher Operational Voltage and Their Charge Storage Mechanism

Biogenic selenium nanoparticles: a comprehensive update on the multifaceted application, stability, biocompatibility, risk, and opportunity

Biogenic selenium nanoparticles (SeNPs) have emerged as promising area of research due to their unique properties and potential multifaceted applications. The biosynthesis of SeNPs through biological methods, such as using microorganism, plant extracts, etc., offers a safe, eco-friendly, and biocompatible approach, compared to traditional chemical synthesis. Recent several studies demonstrated that multifaceted application of SeNPs includes a broad area such as antibacterial, anticancer, antioxidant, antiviral, anti-inflammatory, antidiabetic, and excellent wound healing activity. On the other hand, SeNPs have also shown promising application in sensing of inorganic toxic metals, electrochemistry, agro-industries, aqua-cultures, and in fabrication of solar panels. Additionally, SeNPs capability to enhance the efficacy of traditional antibiotics and act as effective agents against multidrug-resistant pathogens has shown their potential in addressing critical health challenges. Although, the SeNPs exhibit wide applicability, the potential toxicity of Se, particularly in its various oxidative states, necessitates careful assessment of the environmental and health impacts associated with their use. Therefore, understanding the balance between their beneficial properties and potential risks is crucial for its safe applications. This review focuses exclusively on SeNPs synthesized via eco-friendly process, excluding research utilizing other synthesis processes. Moreover, this review aims to offer an overview of the diverse applications, potential risks, stability requirement, and cytocompatibility requirement, and multifaceted opportunities associated with SeNPs. Ultimately, the review bridges a gap in knowledge by providing an updated details of multifaceted applications of SeNPs.

Moisture-Stable CsSnBr2Cl Halide Perovskite: Electrochemical Insights in Aqueous Environments

In this investigation, moisture-stable CsSnBr2Cl nanoparticles were synthesized by incorporating Cl into CsSnBr3 halide perovskite using the hot injection method. Various analyses including XRD, XPS, UV-vis absorbance, photoluminescence, and Mott-Schottky have confirmed that the structural properties, chemical states, optical properties, and electronic band structure of CsSnBr2Cl nanoparticles remain intact even after 75 days of water immersion, thereby conclusively demonstrating their moisture stability. In a three-electrode system, the comparative electrochemical performance of pristine CsSnBr3 nanoparticles and moisture-stable Cl-incorporated CsSnBr2Cl nanoparticles was evaluated in various aqueous electrolytes, including HCl, Na2SO4, and KOH. The results indicate that the CsSnBr2Cl electrode material exhibits superior electrochemical properties, such as a larger integrated cyclic voltammetry (CV) area, a wider potential window, longer charge-discharge times, and lower impedance parameters compared to the pristine CsSnBr3 nanoparticles. The electrochemical performance of CsSnBr2Cl nanoparticles was evaluated for potential applications in batteries, supercapacitors, fuel cells, and water splitting, with a focus on reaction kinetics, charge storage mechanisms, and impedance parameters. The electrochemical properties of the nanoparticles were assessed using a three-electrode configuration across various 0.5 M aqueous electrolytes (HCl, Na2SO4, and KOH). In HCl, the nanoparticles demonstrated impressive charge storage capability, achieving a capacitance of 474 F g-1 at 1 A g-1, affirming their suitability for energy storage devices. In Na2SO4(aq.), the nanoparticles exhibited excellent stability for supercapacitors, operating up to 1.6 V without significant oxygen evolution. Notably, in KOH, they demonstrated potential as effective water-splitting electrodes. The practical applicability of the nanoparticles was evaluated using a symmetric two-electrode configuration with HCl and Na2SO4 electrolytes. The capacitance values were 117 F g-1 in HCl and 70 F g-1 in Na2SO4 at 1 A g-1. Notably, after 5000 GCD cycles in HCl(aq.), the nanoparticles retained 93% of their capacitance and maintained 91% Coulombic efficiency. They also demonstrated stable operation across a temperature range of 3 to 60 °C, achieving an energy density of 5.83 W h kg-1 at a power density of 600 W kg-1. This study emphasizes the considerable potential of CsSnBr2Cl nanoparticles in advancing electrochemical energy storage technologies and sets a solid foundation for future research and development in metal halide perovskites.

Glutathione-Mediated Synthesis of WO3 Nanostructures with Controllable Morphology/Phase for Energy Storage, Photoconductivity, and Photocatalytic Applications

Developing an improved synthesis method that controls the morphology and crystal phase remains a substantial challenge. Herein, we report phase and morphology-controlled hydrothermal synthesis of tungsten oxides by varying acid concentration and utilizing glutathione (GSH) as a structural directing agent, together with the exploration of their applications in supercapacitors, photoconductivity, and photocatalysis. Orthorhombic hydrated tungsten oxide (WO3·0.33H2O) with nonuniform block and plate-like morphology was obtained at 3 M hydrochloric acid (HCl). In contrast, nonhydrated monoclinic tungsten oxide (WO3) with smaller rectangular blocks was obtained at 6 M HCl. Further, the addition of GSH results in an increase in the surface area of the materials along with a narrowing of the band gap. Moreover, it plays a pivotal role in regulating the morphology through oriented attachments, Ostwald ripening, and the self-assembly of WO3 nuclei. GHTO and GTO polymorphs showed pseudocapacitive behavior with the highest specific capacitances of 450 and 300 F g-1 at 0.5 A g-1, maintaining 94 and 92% retention stability, respectively, over 1000 cycles at 2 A g-1. Also, the synthesized materials displayed favorable photoconductivity under light irradiation, implying potential utilization in photovoltaic applications. Moreover, these materials exhibited remarkable photocatalytic performance in the degradation of methylene blue (MB) dye, establishing themselves as highly effective photocatalysts. Therefore, nanostructured tungsten oxide showcases its versatility, rendering it an appealing candidate for energy storage, photovoltaic systems, and photocatalysis.

Optimizing Performance in Supercapacitors through Surface Decoration of Bismuth Nanosheets

Bismuth (Bi) exhibits a high theoretical capacity, excellent electrical conductivity properties, and remarkable interlayer spacing, making it an ideal electrode material for supercapacitors. However, during the charge and discharge processes, Bi is prone to volume expansion and pulverization, resulting in a decline in the capacitance. Deposition of a nonmetal on its surface is considered an effective way to modulate its morphology and electronic structure. Herein, we employed the chemical vapor deposition technique to fabricate Se-decorated Bi nanosheets on a nickel foam (NF) substrate. Various characterizations indicated that the deposition of Se on Bi nanosheets regulated their surface morphology and chemical state, while sustaining their pristine phase structure. Electrochemical tests demonstrated that Se-decorated Bi nanosheets exhibited a 51.1% improvement in capacity compared with pristine Bi nanosheets (1313 F/g compared to 869 F/g at a current density of 5 A/g). The energy density of the active material in an assembled asymmetric supercapacitor could reach 151.2 Wh/kg at a power density of 800 W/kg. These findings suggest that Se decoration is a promising strategy to enhance the capacity of the Bi nanosheets.

Fabrication and Characterization of a Poly(3,4-ethylenedioxythiophene)@Tungsten Trioxide-Graphene Oxide Hybrid Electrode Nanocomposite for Supercapacitor Applications

With the rapid development of nanotechnology, the study of nanocomposites as electrode materials has significantly enhanced the scope of research towards energy storage applications. Exploring electrode materials with superior electrochemical properties is still a challenge for high-performance supercapacitors. In the present research article, we prepared a novel nanocomposite of tungsten trioxide nanoparticles grown over supported graphene oxide sheets and embedded with a poly(3,4-ethylenedioxythiophene) matrix to maximize its electrical double layer capacitance. The extensive characterization shows that the poly(3,4-ethylenedioxythiophene) matrix was homogeneously dispersed throughout the surface of the tungsten trioxide-graphene oxide. The poly(3,4-ethylenedioxythiophene)@tungsten trioxide-graphene oxide exhibits a higher specific capacitance of 478.3 F·g-1 at 10 mV·s-1 as compared to tungsten trioxide-graphene oxide (345.3 F·g-1). The retention capacity of 92.1% up to 5000 cycles at 0.1 A·g-1 shows that this ternary nanocomposite electrode also exhibits good cycling stability. The poly(3,4-ethylenedioxythiophene)@tungsten trioxide-graphene oxide energy density and power densities are observed to be 54.2 Wh·kg-1 and 971 W·kg-1. The poly(3,4-ethylenedioxythiophene)@tungsten trioxide-graphene oxide has been shown to be a superior anode material in supercapacitors because of the synergistic interaction of the poly(3,4-ethylenedioxythiophene) matrix and the tungsten trioxide-graphene oxide surface. These advantages reveal that the poly(3,4-ethylenedioxythiophene)@tungsten trioxide-graphene oxide electrode can be a promising electroactive material for supercapacitor applications.

Enhanced Performance of WO3/SnO2 Nanocomposite Electrodes with Redox-Active Electrolytes for Supercapacitors

For effective supercapacitors, we developed a process involving chemical bath deposition, followed by electrochemical deposition and calcination, to produce WO₃/SnO₂ nanocomposite electrodes. In aqueous solutions, the hexagonal WO₃ microspheres were first chemically deposited on a carbon cloth, and then tin oxides were uniformly electrodeposited. The synthesized WO₃/SnO₂ nanocomposite was characterized by XRD, XPS, SEM, and EDX techniques. Electrochemical properties of the WO₃/SnO₂ nanocomposite were analyzed by cyclic voltammetry, galvanostatic charge-discharge tests, and electrochemical impedance spectroscopy in an aqueous solution of Na₂SO₄ with/without the redox-active electrolyte K₃Fe(CN)₆. K₃Fe(CN)₆ exhibited a synergetic effect on the electrochemical performance of the WO₃/SnO₂ nanocomposite electrode, with a specific capacitance of 640 F/g at a scan rate of 5 mV/s, while that without K₃Fe(CN)₆ was 530 F/g. The WO₃/SnO₂ nanocomposite catalyzed the redox reactions of [Fe(CN)₆]³/[Fe(CN)₆]^4- ions, and the [Fe(CN)₆]^3-/[Fe(CN)₆]^4- ions also promoted redox reactions of the WO₃/SnO₂ nanocomposite. A symmetrical configuration of the nanocomposite electrodes provided good cycling stability (coulombic efficiency of 99.6% over 2000 cycles) and satisfied both energy density (60 Whkg^-1) and power density (540 Wkg^-1) requirements. Thus, the WO₃/SnO₂ nanocomposite prepared by this simple process is a promising component for a hybrid pseudocapacitor system with a redox-flow battery mechanism.

Efficient charge separation and improved photocatalytic activity in Type-II & Type-III heterojunction based multiple interfaces in BiOCl0.5Br0.5-Q: DFT and Experimental Insight

The nanostructured, inner-coupled Bismuth oxyhalides (BiOX0.5X'0.5; X, X' = Cl, Br, I; X≠X') heterostructures were prepared using Quercetin (Q) as a sensitizer. The present study revealed the tuning of the band properties of as-prepared catalysts. The catalysts were characterized using various characterization techniques for evaluating the superior photocatalytic efficiency and a better understanding of elemental interactions at interfaces formed in the heterojunction. The material (BiOCl0.5Br0.5-Q) reflected higher degradation of MO (about 99.85%) and BPA (98.34%) under visible light irradiation than BiOCl0.5I0.5-Q and BiOBr0.5I0.5-Q. A total of 90.45 percent of total organic carbon in BPA was removed after visible light irradiation on BiOCl0.5Br0.5-Q. The many-fold increase in activity is attributed to the formation of multiple interfaces between halides, conjugated π-electrons and multiple -OH groups of quercetin (Q). The boost in degradation efficiency can be attributed to the higher surface area, 2-D nanostructure, inhibited electron-hole recombination, and appropriate band-gap of the heterostructure. Photo-response of BiOCl0.5Br0.5-Q is higher compared to BiOCl0.5I0.5-Q and BiOBr0.5I0.5-Q, indicating better light absorption properties and charge separation efficiency in BiOCl0.5Br0.5-Q due to band edge position. First-principles Density Functional Theory (DFT) based calculations have also provided an insightful understanding of the interface formation, physical mechanism, and superior photocatalytic performance of BiOCl0.5Br0.5-Q heterostructure over other samples.

Dual Metal-Loaded Porous Carbon Materials Derived from Silk Fibroin as Bifunctional Electrocatalysts for Hydrogen Evolution Reaction and Oxygen Evolution Reaction

Developing electrocatalysts with high efficiency and long-term stability for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is significant to massively generate hydrogen energy by water splitting. In this work, cobalt and tungsten dual metal-loaded N-doped porous carbon electrocatalysts derived from silk fibroin were successfully prepared through facile carbonization and chemical activation by KCl and applied as efficient electrocatalysts for HER and OER. After chemical activation, the resulting catalysts present a unique hierarchical porous structure with micro-, meso-, and macropores, which is able to expose more implantation sites for catalytic active metals and will in turn promote the efficient diffusion of the electrolyte. The catalyst under the optimized condition (CoW@ACSF) has a specific area of 326.01 m² g^-1. The overpotential at a current density of 10 mA cm ^-2 of CoW@ACSF is 138.42 ± 10.39 mV toward HER and 492.05 ± 19.04 mV toward OER. Furthermore, the overpotential only increases 101.2 mV toward HER and 66.00 mV toward OER after the long-term stability test of chronopotentiometric test over 10 h, which confirms the excellent stability of the CoW@ACSF, owing to its unique carbon shell structure. This work gives an insight into the design and engineering of silk fibroin-derived carbon materials for electrocatalysis toward HER and OER.

Synthesis of the cathode and anode materials from discarded surgical masks for high-performance asymmetric supercapacitors

Advanced carbon-based electrode materials derived from wastes are essential to high-performance supercapacitors due to their abundance and sustainability. In this work, we fabricate novel cathodes and anodes based on discarded surgicalmask-derived carbon (DSM-C). Discarded surgicalmasks are good candidates for carbon-based electrode materials due to their unique fibrous structure and simple composition compared to conventional biomass sources. Benefiting from the excellent electrical conductivity of DSM-C and abundant redox reactions from nickel oxide (NiO), the electrochemical performances of NiO/DSM-C composites have been greatly improved. Specifically, the DSM-C and NiO/DSM-C electrodes show high specific capacitances of 240 F g^-1 and 496 F g^-1 at 1 A g^-1 respectively, and excellent rate capability. Moreover,asymmetric supercapacitors (ASCs) are assembled using DSM-C and NiO/DSM-C as anodes and cathodes, respectively. They deliver a high energy density of 57 Wh kg^-1 at a power density of 702 W kg^-1, accompanied by superior cycling stability (98.5% capacitance retention after 10,000 cycles). This work shows prospective applications of DSM-C as an electrode material for energy storage systems.