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With the emergence of new technologies, wearable and portable devices become essential tools for various applications, which are flexibly designed. In this situation, flexible supercapacitors with fast charge and discharge cycles are needed as their power source. This study introduces the flexible pseudocapacitor electrode fabricated by electrodeposition of manganese oxide (MnO2) onto heat‐treated hydrophilic buckypaper (BP) molded on polydimethylsiloxane (PDMS). Here, the heat treatment of BP that is optimized by a proper adoption of thermogravimetric analysis is performed to enhance the electrodeposition efficiency of MnO2. Then, proper hydrophilicity of the heat‐treated BP (H‐BP) and successful preparation of MnO2/H‐BP@PDMS electrode is well confirmed by electrochemical, spectroscopical, and optical measurements. In their evaluations, it is found that heat treatment of BP is more important factor than electrodeposition time to improve the electrodeposition efficiency of MnO2 under the same aqueous electrolyte. With that, such optimally prepared MnO2/H‐BP@PDMS electrode shows a high electrical double layer and excellent specific capacitance of 1.31 F/cm2 at 1 mA/cm2, which are better results than those of other electrodes. [ABSTRACT FROM AUTHOR]

A novel polybenzimidazole (PBI)‐based trilayer membrane assembly is developed for application in vanadium redox flow battery (VRFB). The membrane comprises a 1 µm thin cross‐linked poly[2,2′‐(p‐oxydiphenylene)−5,5′‐bibenzimidazole] (OPBI) sandwiched between two 20 µm thick porous OPBI membranes (p‐OPBI) without further lamination steps. The trilayer membrane demonstrates exceptional properties, such as high conductivity and low area‐specific resistance (ASR) of 51 mS cm−1 and 81 mΩ cm2, respectively. Contact with vanadium electrolyte increases the ASR of trilayer membrane only to 158 mΩ cm2, while that of Nafion is 193 mΩ cm2. VO2+ permeability is 2.73 × 10−9 cm2 min−1, about 150 times lower than that of Nafion NR212. In addition, the membrane has high mechanical strength and high chemical stability against VO2+. In VRFB, the combination of low resistance and low vanadium permeability results in excellent performance, revealing high Coulombic efficiency (>99%), high energy efficiency (EE; 90.8% at current density of 80 mA cm−2), and long‐term durability. The EE is one of the best reported to date. [ABSTRACT FROM AUTHOR]

Various sensors and electronic devices are recently developed to monitor human health in mechanically flexible or even stretchable forms for intimate contact with non‐flat curvilinear surfaces of the human body. For successful operation of these devices, finding a proper way to electrically power them is very important. In this work, glucose/oxygen fueled enzymatic biofuel cells (EBFCs) based on microfluidic structured elastomeric polydimethylsiloxane substrate with wrinkled gold (Au) electrodes are suggested for power supply. For doing that, firstly, bottom surface of microfluidic channel is covered with buckled Au electrodes for stretchability. By microfluidic design showing capillary imbibition through fluidic channels, loading of catalyts is promoted. Interestingly, buckled Au electrodes induce much better anodic and cathodic reaction rates than those of non‐buckled Au electrodes by 25% and 33%, respectively. This is because surface area and the amount of catalyst loading in electrodes increase by Au wrinkling. In evaluations of EBFCs using the buckled Au electrodes, maximum power density reaches 7.1 ± 0.64 µW cm−2, while they show decent performance of 5.4 ± 0.49 µW cm−2 even under external stretching. Taken together, it is corroborated that such proposed stretchable EBFCs are alternative for providing electrical power in wearable or implantable devices. [ABSTRACT FROM AUTHOR]

In this study, a new cathodic catalyst including hemin catalyzing the H2O2 reduction reaction (HPRR) is suggested to improve the performance of flow-type hydrogen peroxide fuel cells (HPFCs). To develop the hemin-based catalyst showing excellent HPRR reactivity, buckypaper (BP) and polyethyleneimine (PEI) are used, and it is proved that the final [BP/hemin]/PEI/hemin catalyst has excellent catalytic activity in terms of current and onset potential for the HPRR. To evaluate the effect of the catalyst on the performance of HPFC, BP/hemin and BP/PEI/hemin catalysts as the control groups are fabricated and compared. When [BP/hemin]/PEI/hemin is used, the amount of immobilized hemin and the reactivity of the HPRR increase due to the interstitial pores of the carbon nanotube network. Furthermore, its onset potential increases due to the formation of the coordinate bond between the iron core within hemin and the axial ligand within PEI. For preparing membraneless HPFCs, flexible materials such as hemin-modified BP, carbon cloth and polyethylene terephthalate are used, and its open circuit potential and maximum power density are 0.171 ± 0.012 V and 90.7 ± 6.88 μW cm−2 when 0.1 M H2O2 is injected. These results are far better than those of other previous studies. [ABSTRACT FROM AUTHOR]