In this study, a facile and environmentally friendly method was used to prepare a freestanding supercapacitor electrode displaying excellent areal capacitance and good cycle life performance. First, we prepared polypyrrole nanoparticles (PPyNP) through a simple in situ chemical polymerization using the plant-derived material curcumin as a bioavailable template. A PPyNP/f-CNT freestanding composite electrode of high mass loading (ca. 14 mg cm^–2) was prepared after blending the mixtures of the prepared PPyNP and functionalized CNTs (f-CNTs). The performance of the as-prepared material as a supercapacitor electrode was evaluated in a three-electrode setup using aqueous 1 M H₂SO₄ as the electrolyte. The PPyNP/f-CNT freestanding composite electrode exhibited a high areal capacitance of 4585 mF cm^–2 and a corresponding volumetric capacitance of 176.35 F cm^–3 at a current density of 2 mA cm^–2. A symmetric all-solid-state supercapacitor assembled using two identical pieces of PPyNP/f-CNT composite electrodes exhibited maximum areal energy and power density of 129.24 μW h cm^–2 and 12.5 mW cm^–2, respectively. Besides, this supercapacitor device exhibited good cycle life performance, with 79.03% capacitance retention after 10,000 charge/discharge cycles. These results suggest practical applications for these PPyNP/f-CNT freestanding composite electrode-based symmetric all-solid-state supercapacitors.

In this study, polypyrrole (PPy) having a unique hollow tubular structure was prepared through a simple and scalable one-step method of in situ chemical oxidative polymerization, employing curcumin, a plant-derived material, as a readily removable and eco-friendly template. PPy tubes (PPyT: PPyC1T1, PPyC1T2, PPyC1T4, PPyC2T2, and PPyC3T2) prepared under various conditions were then combined with functionalized carbon nanotubes (f-CNTs) to form freestanding electrodes. Among the tested composite electrodes, the PPyC3T2/f-CNT freestanding electrode exhibited the greatest morphological uniformity, a favorable hierarchical porous structure, the largest surface area, and excellent electrochemical properties. A record areal capacitance of 11 830.4 mF cm⁻² at a current density of 2 mA cm⁻² was obtained for the PPyC3T2/f-CNT-thick freestanding electrode at a high mass loading of 30 mg cm⁻². In addition, a symmetric supercapacitor fabricated using the PPyC3T2/f-CNT-thick freestanding electrode exhibited an excellent areal capacitance (2732 mF cm⁻² at a current density of 2 mA cm⁻²), an outstanding cycling stability (retention of 118.18% of its initial capacitance after 12 500 charge/discharge cycles), and a high energy density (242.84 μW h cm⁻²) and maximum power density (129.35 mW cm⁻²). These characteristics highlight the potential applicability of PPyT/f-CNT freestanding electrodes in high-performance supercapacitors.

The Conducting of polymers belongs to the class of polymers exhibiting excellence in electrical performances because of their intrinsic delocalized π- electrons and their tunability ranges from semi-conductive to metallic conductive regime. Conducting polymers and their composites serve greater functionality in the application of strain and pressure sensors, especially in yielding a better figure of merits, such as improved sensitivity, sensing range, durability, and mechanical robustness. The electrospinning process allows the formation of micro to nano-dimensional fibers with solution-processing attributes and offers an exciting aspect ratio by forming ultra-long fibrous structures. This review comprehensively covers the fundamentals of conducting polymers, sensor fabrication, working modes, and recent trends in achieving the sensitivity, wide-sensing range, reduced hysteresis, and durability of thin film, porous, and nanofibrous sensors. Furthermore, nanofiber and textile-based sensory device importance and its growth towards futuristic wearable electronics in a technological era was systematically reviewed to overcome the existing challenges.

In this study, the vanadium pentoxide (V₂O₅), functionalized carbon nanotubes (f-CNT), and polypyrrole (PPy) based composites films have been prepared through a facile synthesis method and their electrochemical performance were evaluated as freestanding negative electrodes of supercapacitor. A hydrous V₂O₅ gel prepared by treating V₂O₅ powder with H₂O₂ was mixed with f-CNT to obtain V₂O₅/f-CNT composite film. V₂O₅/f-CNT composite was then coated with PPy through vapor phase polymerization method. The PPy deposited on the V₂O₅/f-CNT prevented the dissolution of V₂O₅ and thus resulted in an improved the capacitance and cycle life stability for V₂O₅/f-CNT/PPy composite electrode. V₂O₅/f-CNT/PPy freestanding negative electrode exhibited a high areal capacitance value (1266 mF cm⁻² at a current density of 1 mA cm⁻²) and good cycling stability (83.0% capacitance retention after 10,000 charge-discharge cycles). The superior performance of the V₂O₅/f-CNT/PPy composite electrode can be attributed to the synergy between f-CNT with high conductivity and V₂O₅ and PPy with high-energy densities. Thus, V₂O₅/f-CNT/PPy composite based electrode can effectively mitigate the drawbacks of the low specific capacitance of CNTs and the poor cycling life of V₂O₅.

A highly porous freestanding supercapacitor electrode has been fabricated through a simple, inexpensive, bulk-scalable, and environmentally friendly method, without using any extra current collector, binder, or conducting additive. Benefiting from its unique micro-tubular hollow structure with a thin cell wall and large lumen, kapok fiber (KF) was used herein as a low-cost template for the successive growth of polypyrrole (PPy) through in situ chemical polymerization. This PPy-coated KF (KF@PPy) was blended with functionalized carbon nanotubes (f-CNTs) to form freestanding conductive films (KF@PPy/f-CNT) through a simple dispersion and filtration method. The hybrid film featuring the optimal composition exhibited an outstanding areal capacitance of 1289 mF cm⁻² at a scan rate of 5 mV s⁻¹. Moreover, an assembled all-solid-state symmetric supercapacitor featuring a PVA/H₂SO₄ gel electrolyte exhibited not only areal capacitances as high as 258 mF cm⁻² (at a scan rate of 5 mV s⁻¹) but also excellent cycling stability (97.4% of the initial capacitance after 2500 cycles). Therefore, this efficient, low-cost, scalable green synthesis strategy appears to be a facile and sustainable way of fabricating high-performance flexible supercapacitors incorporating a renewable cellulose material.