High Energy Density Supercapacitors: An Overview of Efficient Electrode Materials, Electrolytes, Design, and Fabrication.

Supercapacitors (SCs) are potentially trustworthy energy storage devices, therefore getting huge attention from researchers. However, due to limited capacitance and low energy density, there is still scope for improvement. The race to develop novel methods for enhancing their electrochemical characteristics is still going strong, where the goal of improving their energy density to match that of batteries by increasing their specific capacitance and raising their working voltage while maintaining high power capability and cutting the cost of production. In this light, this paper offers a succinct summary of current developments and fresh insights into the construction of SCs with high energy density which might help new researchers in the field of supercapacitor research. From electrolytes, electrodes, and device modification perspectives, novel applicable methodologies were emphasized and explored. When compared to conventional SCs, the special combination of electrode material/composites and electrolytes along with their fabrication design considerably enhances the electrochemical performance and energy density of the SCs. Emphasis is placed on the dynamic and mechanical variables connected to SCs' energy storage process. To point the way toward a positive future for the design of high-energy SCs, the potential and difficulties are finally highlighted. Further, we explore a few important topics for enhancing the energy densities of supercapacitors, as well as some links between major impacting factors. The review also covers the obstacles and prospects in this fascinating subject. This gives a fundamental understanding of supercapacitors as well as a crucial design principle for the next generation of improved supercapacitors being developed for commercial and consumer use.

The effects of functionalized graphene oxide on the thermal and mechanical properties of liquid crystalline polymers.

Herein, we report a robust approach for the selective covalent functionalization of graphene oxide (GO) with 4-hydroxybenzoic acid (HBA) for developing polymeric nanocomposites based on liquid crystalline polymers (LCPs). The functionalization of GO with HBA was confirmed by Raman spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, and X-ray diffraction (XRD) spectroscopy. The surface morphology of GO and functionalized GO (FGO) was studied using field emission scanning electron microscopy (FE-SEM). Furthermore, the interactions between FGO and LCPs have been investigated by FT-IR spectroscopy, whereas dispersion of GO and FGO in the LCP matrix was analyzed by FE-SEM. The better dispersion of FGO can be attributed to the hydrogen bonding and π-π stacking interactions between FGO and LCPs. Our results showed that even the addition of 5 wt% FGO in the LCP matrix significantly enhances the tensile strength and storage modulus of the pristine LCPs by 84% and 78% respectively. Compared to neat LCPs, FGO incorporated composites also demonstrate an improvement in the melting temperature (Tm) by 11 °C and glass transition temperature (Tg) by 12 °C. Furthermore, thermogravimetric analysis (TGA) was performed to evaluate the thermal stability of the composite. The 5 and 50% decomposition temperature for the LCP/FGO nanocomposites (containing 5 wt% FGO) increased by 75 °C and 107 °C respectively.

Effect of terephthalic acid functionalized graphene oxide on the molecular interaction, and mechanical and thermal properties of Hytrel polymer.

We report the effect of incorporating functionalized graphene oxide (terephthalic acid functionalized GO; GO-g-TPA) on the thermal and mechanical properties of Hytrel (HTL; a thermoplastic elastomeric polymer). Initially, the synthesis of GO-g-TPA was performed via chemical methods and subsequently characterized using various spectroscopic and imaging techniques. The melt mixing technique was executed in preparing the nanocomposites of HTL/GO and HTL/GO-g-TPA. An excellent GO dispersion was observed in the HTL polymeric matrix, which could be attributed to the significant effect of hydrogen bonding and π-π interaction between the HTL and GO-g-TPA. As a result of incorporating GO and GO-g-TPA into the HTL matrix, the overall mechanical and thermal properties of the nanocomposites were significantly improved. For the HTL/5 wt% GO-g-TPA nanocomposite, the tensile strength and storage modulus significantly increased by 61% and 224%, respectively. In addition, the melting temperature and crystalline temperature are increased by a notable 20 °C and 21 °C, respectively. Thus, the current study found that by improving the dispersion ability of the GO sheets, the properties of the HTL can be significantly enhanced and the prepared composite materials can be relevant for a wide range of applications including sports goods, hose jackets, wire and cable jackets, electronics, fluid power, sheeting belting seals, and footwear, etc.

Self-healing nanocomposites via N-doped GO promoted "click chemistry".

N-doped graphene stabilized Cu(I)-catalyzed self-healing nanocomposites are developed. This study found the use of N-doped graphene as both a nanostructured material for enhancing mechanical and conductive properties and a catalyst promoter (a scaffold for catalytic copper(I) particles), helpful to trigger self-healing via "click chemistry". Due to an increase in electron density on nitrogen atom doping, including the coordination of N-doped rGO with Cu+ ions, nitrogen-doped graphene-supported copper particles demonstrate a higher reaction yield at room temperature without adding any external ligand/base. In this study, only one component (an azide moiety containing a healing agent) was encapsulated, whereas another component (an alkyne moiety containing a healing agent) was as such (without encapsulation) homogeneously dispersed in a matrix. Triggered capsule rupture then induces the contact of the healing agents with the N-doped graphene-based catalyst and the alkyne molecules dispersed in the matrix, inducing a "click"-reaction, allowing onsite damage to be repaired as determined by mechanical measurements entirely. Tensile measurements were also performed using molecular dynamics (MD) simulations to support the findings. Given the enormous importance of autonomic repair of materials damage, this concept here reports a trustworthy and reliable chemical system with a high level of robustness.

Activating agent-driven hierarchical nano-porous structure in mustard oil-derived carbon soot for supercapacitive application.

In the present paper, activated nano-carbon soot is derived from atmospheric flame combustion of thymol-mustard oil followed by activation with potassium hydroxide (KOH) to produce micro- and mesoporous interiors. Different forms of activated nano-carbon soot are produced by using different weight percentage ratios 1:1, 1:3, and 1:5 of precursor carbon soot (CS) to KOH and named CS11, CS13, and CS15, respectively. An increase in specific surface area and average pore volume is observed with an increase in the amount of KOH with the hierarchical network having balanced micropores as well as mesopores in CS15. The electrochemical performance of prepared activated nano-carbon soot is further investigated by the fabrication of a symmetric electric double-layer solid-state supercapacitor (SC) device utilizing a 6 M KOH electrolyte. The CS15-based device displays the highest specific capacitance (Csp) of 226.20 F/g at a current density of 0.5 A/g with energy density (Ed) 31.42 Wh/kg at a power density (Pd) of 250 W/kg. The Csp, Ed, and Pd are found to be higher than activated nano-carbon soot reported in the literature. Further, three-coin cells are fabricated using CS15 which are tested in series combination with yellow light emitting diode (LED) and are found to be able to glow LED for ~ 5 min 25 s.

Ferulic acid-g-tamarind gum/guar gum based in situ gel-forming powders as wound dressings.

The current research endeavour aimed to synthesize ferulic acid grafted tamarind gum/guar gum (FA-g-TG/GG) based powders as wound dressings, which could form in situ gels upon contact with wound exudates. In this context, variable amounts of FA were initially grafted with TG via the Steglich esterification reaction protocol and the resulting conjugates were subsequently amalgamated with GG and lyophilized to produce dry powders (F-1 - -F-3) with average particle size within 5.10-5.54 µm and average angle of repose ∼30°. These powders were structurally characterized with 1H NMR, FTIR, DSC, TGA, XRD and SEM analyses. Pristine TG, FA-g-TG and FA-g-TG/GG powders (F-2) revealed their distinct morphological structures and variable negative zeta potential values (-11.06 mV-25.50 mV). Among various formulation (F-1-F-3), F-2 demonstrated an acceptable powder-to-gel conversion time (within 20 min), suitable water vapour transmission rates (WVTR, 2564.94 ± 32.47 g/m2/day) and excellent water retention abilities and swelling profiles (4559.00 ± 41.57 %) in wound fluid. The powders were cytocompatible and conferred antioxidant activities. The powders also displayed fibroblast cell proliferation, migration and adhesion properties, implying their wound-healing potentials. Thus, the developed in situ gel-forming powders could be employed as promising dressings for wound management.

Mass scale synthesis of graphene nanosheets using waste cardboard for application in perovskite solar cells and supercapacitors.

Advanced graphene-based materials have been proficiently incorporated into next-generation solar cells and supercapacitors because of their high electrical conductivity, large surface area, excellent charge-transport ability, and exceptional optical properties. Herein, we report the synthesis of graphene nanosheets (GNs) from waste cardboard via pyrolysis, with ethyl alcohol as the growth initiator. Additionally, we demonstrated the use of GNs in energy conversion and storage applications. Using the GN electrode in perovskite solar cells resulted in an excellent power conversion efficiency of ∼10.41 % for an active area of 1 cm2, indicating an enhancement of approximately 27 % compared to conventional electrodes. Furthermore, the GNs were used as active electrode materials in supercapacitors with excellent electrochemical performance and a high gravimetric specific capacitance of 167.5 F/g at a scan rate of 2 mV/s. The developed GNs can be efficiently used for energy storage, conversion, and electrochemical sensing applications.

Polymer nanocomposite hydrogels exhibiting both dynamic restructuring and unusual adhesive properties.

Polymer nanocomposite (NC) hydrogels exhibiting both dynamic restructuring and unusual adhesive properties in wet and dry states have been prepared in an efficient and straightforward way via free radical polymerization of poly(ethylene glycol) methyl ether acrylate (PEG) in the presence of silane-modified sodium montmorillonite (NaMMT). The dynamic restructuring of the NC gel has been demonstrated by almost instant recovery of mechanical properties, such as storage modulus, loss modulus, and damping tan δ (at 0.025 strain) by 60-110% after being stressed to the point of gel failure. Furthermore, the dry NC gel showed exceptional thermal and mechanical stability during a heating and cooling cycle between 25 and 110 °C, with only slightly decreases followed by at least 30% increases in both moduli, while tan δ remained nearly unchanged. The NC gel in dry state could repeatedly adhere to various surfaces such as steel, glass, plastic, etc., and detach from the surface without being broken and leaving little contamination behind. This unique adhesive characteristic was characterized by high storage modulus, loss modulus (kPa), and tan δ (>0.6) corresponding to high cohesive, adhesive, and tacking properties of pressure-sensitive adhesives (PSAs). Finally, a reversible network structure formed by PEO interpenetrating within 3-dimentional (3-D) silica network was proposed to be responsible for the dynamic restructuring and the unique adhesive behaviors observed in the NC gel, and the 3-D network structure was investigated by XRD, FTIR, and DSC measurements. For this 3-D network structure, we suggest that the flexibility of PEO could allow PEO side chains to contact with various surfaces by either PEO segments or methoxy end groups via weak physical interactions, such as van der Waals interactions or hydrogen bonding, whereas the reversible network structure contributes to the recovery of strength and shape after the gel failure.

Polyamidoamine dendrimer decorated graphene oxide as a pH-sensitive nanocarrier for the delivery of hydrophobic anticancer drug quercetin: a remedy for breast cancer.

OBJECTIVES: The aim of this study was to investigate the potential of poly(amido amine) (PAMAM) dendrimer decorated graphene oxide (GO) based nanocarrier for targeted delivery of a hydrophobic anticancer drug, quercetin (QSR). METHODS: GO-PAMAM was successfully synthesized by covalent bonding between GO and NH2-terminated PAMAM dendrimer (zero generation). To investigate drug loading performance, QSR was loaded on the surface of GO as well as GO-PAMAM. Further, the release behaviour of QSR-loaded GO-PAMAM was studied. Finally, an in-vitro sulforhodamine B assay was performed in HEK 293T epithelial cells and MDA MB 231 breast cancer cells. KEY FINDINGS: It was observed that GO-PAMAM shows higher QSR loading capacity compared to GO. Also, synthesized nanocarrier exhibits controlled as well as pH-responsive release of QSR and the amount of QSR released at pH 4 was approximately two times higher than the release at pH 7.4. Furthermore, GO-PAMAM was found to be biocompatible for HEK 293T cells, and a high cytotoxic effect was observed for QSR-loaded GO-PAMAM on MDA MB 231 cells. CONCLUSIONS: The present investigation highlights the potential application of synthesized hybrid materials as a nanocarrier with excellent loading and controlled releasing efficiency for the delivery of the hydrophobic anticancer drug.

Facile fabrication and application of highly efficient reduced graphene oxide (rGO)-wrapped 3D foam for the removal of organic and inorganic water pollutants.

The pace of water contamination is increasing daily due to expanding industrialisation. Finding a feasible solution for effectively remediating various organic and inorganic pollutants from large water bodies remains challenging. However, a nano-engineered advanced hybrid material could provide a practical solution for the efficient removal of such pollutants. This work has reported the development of a highly efficient and reusable absorbent comprising a porous polyurethane (PU) and reduced graphene oxide (rGO) nanosheets (rGOPU) for the removal of different organic oils (industrial oil, engine oil and mustard oil), dyes (MB, MO, RB, EY and MV) and heavy metals (Pb(II), Cr(VI), Cd(II), Co(II) and As(V)). The structure, morphology and properties of the rGOPU hybrid absorbents were analysed by using Raman spectroscopy, field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Brunner-Emitte-Teller (BET) analysis. The rGOPU possessed both superhydrophobicity and superoleophilicity with water and oil contact angles of about 164° and 0°, respectively. The prepared rGOPU has demonstrated an excellent oil-water separation ability (up to 99%), heavy metals removal efficiency (more than 75%), toxic dye adsorption (more than 55%), excellent recyclability (> 500 times for oils), extraordinary mechanical stability (90% compressible for > 1000 cycles) and high recoverability. This work presents the first demonstration of rGOPU's multifunctional absorbent capacity in large-scale wastewater treatment for effectively removing a wide variety of organic and inorganic contaminants.