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.

Vanadium pentaoxide-doped waste plastic-derived graphene nanocomposite for supercapacitors: a comparative electrochemical study of low and high metal oxide doping.

We report the bulk phase synthesis of graphene sheets using waste plastic (WP) as a precursor following a modified pyrolysis approach. Furthermore, the low and high mass loading of vanadium pentaoxide was performed on graphene sheets in 1 : 10 and 1 : 1 ratios, respectively. Advanced characterization techniques such as Raman spectroscopy, FT-IR spectroscopy, X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA) analysis, and SEM imaging were used to confirm the synthesis of graphene. FT-IR spectroscopy confirmed that the resonating structure affects the bond strength in the composite, which enables peak shifting in the FT-IR spectrum of the composite. Furthermore, bandgap analysis has been performed using UV-Vis spectroscopy, which confirmed the synthesis of the composites. The developed vanadium-doped graphene was used as the active material for the fabrication of supercapacitor electrodes. The electrochemical performance of these devices was evaluated in 1 M H3PO4 solution using cyclic voltammetry (CV), galvanic charge-discharge (GCD) analysis, and electrochemical impedance spectroscopy (EIS). Fabricated cells 1 and 2 showed exceptional specific capacitances of 139.7 F g-1 and 51.2 F g-1 at 5 mV s-1 scan rate, respectively. Cell 1 showed a huge power density of 5312 W kg-1 and an energy density of 19.7 W h kg-1. Conversely, cell 2 showed a comparatively lower power density of 1941 W kg-1 and an energy density of 7.2 W h kg-1 at a 5 mV s-1 scan rate. Moreover, we disclose some brief conclusions on the performance, mechanism, and required modifications that can improve the performance of such devices. This approach can surely help with universal WP problems as well as the development of high-performance supercapacitors.

3D graphene nanosheets from plastic waste for highly efficient HTM free perovskite solar cells.

Herein, we report the first time application of waste plastic derived 3D graphene nanosheets (GNs) for hole transport material (HTM) free perovskite solar cells (PSCs), where 3D GNs have been employed as an electrode dopant material in monolithic carbon electrode based mesoscopic PSCs. Waste plastics were upcycled into high-quality 3D GNs by using two-step pyrolysis processes, where, a nickel (99.99%) metal mesh was taken as the catalytic and degradation template to get an acid free route for the synthesis of 3D GNs. Raman spectroscopy, HRTEM analysis and XRD analysis show the presence of 1-2 graphene layers within the 3D GNs. Further, the optical band gap study has also been performed to analyze the applicability of 3D GNs for PSCs. The optimized device with 3D GNs shows a power conversion efficiency (PCE) of 12.40%, whereas the carbon-based control device shows a PCE of 11.04%. Further, all other device parameters such as short circuit current (J sc), open circuit voltage (V oc) and fill factor (FF) have been improved with the addition of 3D GNs. The performance enhancement in 3D GN doped HTM free PSC solar cells is attributed to the enhancement in conductivity and reduced recombination within the device. Further, the photocurrent study shows that the 3D GN device shows better performance as compared to the reference device due to the larger diffusion current. Thus, the upcycling of waste plastics into 3D GNs and their exploitation for application in energy conversion show an effective and potential way to convert waste into energy.