For hybrid electric vehicles, supercapacitors are an attractive technology which, when used in conjunction with the batteries as a hybrid system, could solve the shortcomings of the battery. Supercapacitors would allow hybrid electric vehicles to achieve high efficiency and better power control. Supercapacitors possess very good power density. Besides this, their charge-discharge cycling stability and comparatively reasonable cost make them an incredible energy-storing device. The manufacturing strategy and the major parts like electrodes, current collector, binder, separator, and electrolyte define the performance of a supercapacitor. Among these, electrode materials play an important role when it comes to the performance of supercapacitors. They resolve the charge storage in the device and thus decide the capacitance. Porous carbon, conductive polymers, metal hydroxide, and metal oxides, which are some of the usual materials used for the electrodes in the supercapacitors, have some limits when it comes to energy density and stability. Major research in supercapacitors has focused on the design of stable, highly efficient electrodes with low cost. In this review, the most recent electrode materials used in supercapacitors are discussed. The challenges, current progress, and future development of supercapacitors are discussed as well. This study clearly shows that the performance of supercapacitors has increased considerably over the years and this has made them a promising alternative in the energy sector.

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This study investigated the solvent effect on the synthesis of Zinc Oxide (ZnO) nanoparticle using sol-gel method. Zinc acetate dihydrate and oxalic acid were used as a chemical precursor for the synthesis of the ZnO nanoparticle considering the effects of various solvents. The effect of using water, propanol, or ethanol as solvent during the synthesis were examined. The resultant gel in the aqueous and organic moderate solvent was thermally cracked into ZnO nanoparticles at 450 °C under atmospheric pressure. The results showed that the solvent type has a significant effect on the morphology and particles size of the ZnO nanoparticles synthesized. Atomic Force Microscopy (AFM) was used to investigate the microstructure of the nanoparticles. The crystalline and chemical structure of the prepared ZnO nanoparticle were studied by X-ray diffraction (XRD) and Fourier Transform Infrared spectroscopy (FTIR). The average diameter of nano-size particles obtained for ethanol, propanol and water are 79.55 nm, 83.86 nm and 85.59 nm, respectively. ZnO particles showed higher degree of crystalline in water compared to other solvents under current investigation. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Alarming levels of greenhouse gas emissions has triggered change in the mode of direction of building material research. In this pursuit, alkali activated binders (AAB), synthesized by activation of industrial by products and natural materials in the presence of highly alkaline solutions, have offered viable alternative to OPC. However, there are quite a number of variables which controls the properties of these binders. Among these parameters, SS/SH ratio and molarity of sodium hydroxide solution plays a very important role in the development of these binders. Therefore, this research investigates the effect of SS/SH ratio, subsequently, molarity of SH solution on the properties of natural pozzolan based AAB. The NP was activated with sodium silicate to sodium hydroxide ratio (SS/SH) between 2.0 to 2.75. Subsequently, the molarity of SH solution was varied between 8 to 14. The development in strength was monitored on the specimens cured at 60 °C. SEM and EDS techniques were used to determine the nature of the binder formed during alkali activation. The results have shown that SS/SH ratio of 2.5 and 14 molar SH solution resulted in higher strength and finer microstructure as compared to others. Also, it was understood that there exists a suitable silica modulus of combined activator which results in higher polymerization.