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1. Vertically Aligned Carbon Nanotubes Grown on Copper Foil as Electrodes for Electrochemical Double Layer Capacitors

   https://doi.org/10.3390/nano15191506  

   Nwanno, Chinaza E; Gotame, Ram Chandra; Watt, John; Kuo, Winson; Li, Wenzhi (October 2025, Nanomaterials)

   This study reports a binder-free, catalyst-free method for fabricating vertically aligned carbon nanotubes (VACNTs) directly on copper (Cu) foil using plasma-enhanced chemical vapor deposition (PECVD) for electrochemical double-layer capacitor (EDLC) applications. This approach eliminates the need for catalyst layers, polymeric binders, or substrate pre-treatments, simplifying electrode design and enhancing electrical integration. The resulting VACNTs form a dense, uniform, and porous array with strong adhesion to the Cu substrate, minimizing contact resistance and improving conductivity. Electrochemical analysis shows gravimetric specific capacitance (Cgrav) and areal specific capacitance (Careal) of 8 F g−1 and 3.5 mF cm−2 at a scan rate of 5 mV/s, with low equivalent series resistance (3.70 Ω) and charge transfer resistance (0.48 Ω), enabling efficient electron transport and rapid ion diffusion. The electrode demonstrates excellent rate capability and retains 92% of its initial specific capacitance after 3000 charge–discharge cycles, indicating strong cycling stability. These results demonstrate the potential of directly grown VACNT-based electrodes for high-performance EDLCs, particularly in applications requiring rapid charge–discharge cycles and sustained energy delivery. 

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2. Electrochemically Stable Carbazole-Derived Polyaniline for Pseudocapacitors

   https://doi.org/10.1021/acsapm.1c01616  

   Almtiri, Mohammed; Dowell, Timothy J.; Giri, Hari; Wipf, David O.; Scott, Colleen N. (March 2022, ACS Applied Polymer Materials)

   Supercapacitor energy storage devices are well suited to meet the rigorous demands of future portable consumer electronics (PCEs) due to their high energy and power densities (i.e., longer battery-life and rapid charging, respectively) and superior operational lifetimes (10 times greater than lithium-ion batteries). To date, research efforts have been narrowly focused on improving the specific capacitance of these materials; however, emerging technologies are increasingly demanding competitive performance with regards to other criteria, including scalability of fabrication and electrochemical stability. In this regard, we developed a polyaniline (PANI) derivative that contains a carbazole unit copolymerized with 2,5-dimethyl-p-phenylenediamine (Cbz-PANI-1) and determined its optoelectronic properties, electrical conductivity, processability, and electrochemical stability. Importantly, the polymer exhibits good solubility in various solvents, which enables the use of scalable spray-coating and drop-casting methods to fabricate electrodes. Cbz-PANI-1 was used to fabricate electrodes for supercapacitor devices that exhibits a maximum areal capacitance of 64.8 mF cm–2 and specific capacitance of 319 F g–1 at a current density of 0.2 mA cm–2. Moreover, the electrode demonstrates excellent cyclic stability (≈ 83% of capacitance retention) over 1000 CV cycles. Additionally, we demonstrate the charge storage performance of Cbz-PANI-1 in a symmetrical supercapacitor device, which also exhibits excellent cyclic stability (≈ 91% of capacitance retention) over 1000 charge–discharge cycles. 

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3. Formation of Ge–GeS core–shell nanostructures via solid-state sulfurization of Ge nanowires

   https://doi.org/10.1039/C8CE00221E  

   Keiser, Courtney; Sutter, Peter; Sutter, Eli (January 2018, CrystEngComm)

   Germanium nanowires (NWs) have attractive properties for a variety of applications, including micro- and optoelectronics, memory devices, solar energy conversion, and energy storage, among others. For applications that involve exposure to air, the poor chemical stability and electronic surface passivation of native oxides have remained a long-standing concern. Termination by sulfur-rich surface layers has emerged as a promising strategy for passivation of planar Ge surfaces. Here we discuss experiments on solid-state sulfurization of Ge nanowires in sulfur vapor at near-ambient pressures and at different temperatures. Combined transmission electron microscopy imaging and chemical mapping establishes that Ge NWs remain intact during vapor-phase reaction with S at elevated temperatures, and show the formation of sulfur-rich shells with T-dependent morphology and thickness on the Ge NW surface. Photoluminescence of ensembles of such core–shell nanowires is dominated by strong emission at ∼1.85 eV, consistent with luminescence of GeS. Cathodoluminescence spectroscopy on individual NWs establishes that this luminescence originates in thin GeS shells formed by sulfurization of the NWs. Our work establishes direct sulfurization as a viable approach for forming stable, wide-bandgap surface terminations on Ge NWs. 

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4. In-situ grown of FeCo2O4 onto 2D-Carbyne coated nickel foam - A newer nanohybrid electrode for high performance supercapacitor

   Dhandapania, Preethi; Balan, Balakrishnan; Dinadayalane; Tandabany; Angaiaha, Subramania (January 2022, Journal of energy storage)

   In this study, we synthesized carbyne by a simple chemical route and then this was coated on nickel foam. On this carbyne coated nickel foam, FeCo2O4 was grown by the solvothermal process to serve as a nanohybrid electrode for supercapacitor applications. This nanohybrid electrode has shown high specific capacitance due to the large surface area, high electrical conductivity and improved rate characteristics. The specific capacitance of FeCo2O4 @ Carbyne nanohybrid electrode was about 2584.8 Fg-1 at the current density of 3 Ag-1. Furthermore, the asymmetric supercapacitor device integrated with FeCo2O4 @ Carbyne and activated carbon (FeCo2O4 @ Carbyne || AC) shows better performance with an energy density of about 96.59 WhKg-1 at a high-power density of 2.25 kW kg-1 with a capacitance decay of about 14.52 % even at 5000 cycles. These outcomes provide a new approach for the development of supercapacitors with superior characteristics. 

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5. Prussian blue-assisted one-pot synthesis of nitrogen-doped mesoporous graphitic carbon spheres for supercapacitors

   https://doi.org/10.1039/C9TA08454A  

   Dassanayake, Arosha C.; Wickramaratne, Nilantha P.; Hossain, Mohammad Akter; Perera, Vindya S.; Jeskey, Jacob; Huang, Songping D.; Shen, Hao; Jaroniec, Mietek (October 2019, Journal of Materials Chemistry A)

   Synthesis of nitrogen doped mesoporous graphitic carbon spheres with dispersed metal oxide nanoparticles using a single temperature treatment step serves as one of the big challenges in materials research. To date only a few reports have been published on the soft-templating synthesis of mesoporous graphitic carbons. The preparation of graphitic carbons with dispersed Fe 2 O 3 using a single carbonization step at relatively low temperatures is yet to be explored. The first phase of this work shows the potential of graphitization of polyvinylpyrrolidine (PVP) stabilized cubic Prussian blue nanoparticles (CPB) in phenolic resin spheres to produce graphitic carbon spheres through a facile Stöber-like method. In the second phase, the Pluronic F127 soft template was used along with PVP stabilized Prussian blue nanoparticles (PB) in carbon spheres to generate mesopores and graphitic domains with uniformly dispersed Fe 2 O 3 nanoparticles in these spheres. Due to the presence of graphitic layers, doped N species and Fe 2 O 3 nanoparticles in the carbon matrix, the yielded carbon spheres feature a high surface area and magnetic properties. Moreover, these graphitic spheres exhibited excellent capacitive behavior with rectangular cyclic voltammetry (CV) profiles and large capacitance up to 247 F g −1 at 1 mV s −1 scan rate in 6 M KOH solution. 

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