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Double‐walled carbon nanotubes (DWNTs) have shown potential as promising alternatives to conventional transparent electrodes owing to their solution processability as well as high conductivity and transparency. However, their DC to optical conductivity ratio is limited by the surrounding surfactants that prevent the p‐doping of the DWNTs. To maximize the doping effectiveness, the surfactants are removed from the DWNTs, with negligible damage to the nanotubes, by calcination in an Ar atmosphere. The effective removal of the surfactants is characterized by various analyses, and the results show that the optimal calcination temperature is 400 °C. The conductivity of the DWNTs films improves when doped by triflic acid. While the conductivity increase of the surfactants‐wrapped DWNT films is 31.9%, the conductivity increase of the surfactants‐removed DWNT is found to be 59.7%. Using the surfactants‐removed, p‐doped, solution‐processed transparent electrodes, inverted‐type perovskite solar cells are fabricated, resulting in a power conversion efficiency of 17.7% without hysteresis. This work advances the application of DWNTs in transparent conductors, as the efficiency obtained is the highest value achieved to date for carbon nanotube electrode‐based perovskite solar cells and solution‐processable transparent electrode‐based solar cells. [ABSTRACT FROM AUTHOR]

In this work a novel method is unfolded to modify carbon felts (CF) to substantially improve the performance of the electrodes for vanadium redox flow batteries (VRFBs). The carbon felt, a well-known electrode material for VRFB, is catalytically etched by cobalt oxide to form carbon nanorods on the surface of the fibers comprising the CF. Unlike conventional multistep processes to grow nano-structures on carbon felts, this method simply involves a thermal treatment of catalyst-loaded felt in air to produce well aligned nanorods on its fibers. The surface morphology is optimized by etching temperature, treatment time and catalyst type. The catalytically etched CF shows an improved surface wettability and an enlarged specific surface area about two times compared to pristine CF that lead to an improvement of kinetics towards vanadium redox reactions. When used as electrode in all-vanadium redox flow battery, the nanorod-structured CF shows around 35% higher charge/discharge rate capability at 150 mA cm −2 and 80% retained-capacity compared to 48% in case of un-etched CF as confirmed by a long run test with a hundred cycles of charge/discharge operation at 50 mA cm −2 . [ABSTRACT FROM AUTHOR]

Abstract: Platinum nanoparticles (Pt NPs) were deposited on a layer-by-layer (LBL) assembled carbon nanotube (CNT) thin film via the spontaneous reduction of H2PtCl6 at the functional defect sites of the CNT surface. This nanostructure was characterized by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The modified electrode can be used for the nonenzymatic detection of cholesterol by chronoamperometry (CA) in neutral PBS. We also studied the optimal number of CNT layer for obtaining high sensitivity. The sensor with 24 bilayer of CNT shows very low detection limit and a wide linear range from 0.005mM to 10mM with a sensitivity of 8.7μAmM−1 cm−2. The result is attributed to the LBL assembled structure and more continuous intercalated pathways for electron transport in LBL assembled CNT film and the fact that the CNT film can provide a larger surface area for Pt NP loading. The sensor has good anti-interferent properties in the presence of glucose, ascorbic acid, and dopamine. [Copyright &y& Elsevier]

Abstract: Polypyrrole (PPy)/carbon nanotube (CNT) composite electrodes are fabricated on ceramic fabrics for electrochemical capacitor applications. The CNTs are grown on the ceramic fabrics by the chemical vapor deposition (CVD) method and PPy is subsequently coated on them by chemical polymerization. The large surface area and high conductivity of the CNTs on the porous ceramic fabrics enhance their energy storage capacity. PPy provides not only additional capacitance as an active material, but also enhances the adhesion between the CNTs and ceramic fabrics. Furthermore, PPy acts as a conducting binder for connecting every individual CNT to increase the capacitance. The morphology of the PPy–CNTs on the ceramic fabrics is confirmed by SEM and TEM, and the electrochemical characteristics are investigated by cyclic voltammetry and galvanostatic charge–discharge tests. [Copyright &y& Elsevier]

Highlights from the article: Electrodes: High-Performance Solution-Processed Double-Walled Carbon Nanotube Transparent Electrode for Perovskite Solar Cells (Adv. Keywords: double-walled nanotubes; indium free; perovskite solar cells; solution-processed electrodes; transparent electrodes Double-walled nanotubes, indium free, perovskite solar cells, solution-processed electrodes, transparent electrodes.

Double‐walled carbon nanotubes are between single‐walled carbon nanotubes and multiwalled carbon nanotubes. They are comparable to single‐walled carbon nanotubes with respect to the light optical density, but their mechanical stability and solubility are higher. Exploiting such advantages, solution‐processed transparent electrodes are demonstrated using double‐walled carbon nanotubes and their application to perovskite solar cells is also demonstrated. Perovskite solar cells which harvest clean solar power have attracted a lot of attention as a next‐generation renewable energy source. However, their eco‐friendliness, cost, and flexibility are limited by the use of transparent oxide conductors, which are inflexible, difficult to fabricate, and made up of expensive rare metals. Solution‐processed double‐walled carbon nanotubes can replace conventional transparent electrodes to resolve such issues. Perovskite solar cells using the double‐walled carbon nanotube transparent electrodes produce an operating power conversion efficiency of 17.2% without hysteresis. As the first solution‐processed electrode‐based perovskite solar cells, this work will pave the pathway to the large‐size, low‐cost, and eco‐friendly solar devices. [ABSTRACT FROM AUTHOR]