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Cross-linked beta alumina nanowires with compact gel polymer electrolyte coating for ultra-stable sodium metal battery
No full textSodium metal batteries have potentially high energy densities, but severe sodium-dendrite growth and side reactions prevent their practical applications, especially at high temperatures. Herein, we design an inorganic ionic conductor/gel polymer electrolyte composite, where uniformly cross-linked beta alumina nanowires are compactly coated by a poly (vinylidene fluoride-co-hexafluoropropylene)-based gel polymer electrolyte through their strong molecular interactions. These beta alumina nanowires combined with the gel polymer layer create dense and homogeneous solid-liquid hybrid sodium-ion transportation channels through and along the nanowires, which promote uniform sodium deposition and formation of a stable and flat solid electrolyte interface on the sodium metal anode. Side reactions between the sodium metal and liquid electrolyte, as well as sodium dendrite formation, are successfully suppressed, especially at 60 degrees C. The sodium vanadium phosphate/sodium full cells with composite electrolyte exhibit 95.3% and 78.8% capacity retention after 1000 cycles at 1C at 25 degrees C and 60 degrees C, respectively
Polymer hydrogel interfaces in electrochemical sensing strategies: A review
No full textHydrogels are hydrophilic polymeric networks prepared by physical or chemical cross-linking of gelator molecules under optimum conditions. Being sensitive to external stimuli, hydrogels are integrated into signal transduction systems for generating possible responses upon interaction with target analytes to study various physiochemical/biochemical molecular recognition processes. In recent times, polymer based hydrogel materials have emerged as unique electrode modifying materials providing highly permeable matrix for easy diffusion of analytes and rapid electron transport. Polymeric architectures of hydrogels can accommodate different nanomaterials within its matrix through suitable interactions to form hydrogel nanocomposites. Further, high biocompatibility of hydrogels facilitates facile encapsulation and cross-linking of bioreceptors (eg. nucleic acid, protein) into polymer matrix and helps to retain their bioactivity during practical applications. Polymer hydrogel materials enable easy prototyping of electrodes using novel printing technologies for designing next generation advanced, flexible and portable bioelectronics with excellent sensing performances. The present article focuses on the implication of polymer hydrogels as high performance electrode materials. Taking relevant examples, nanomaterials incorporated polymer hydrogel based chemical sensors and bioreceptors embedded biosensors have been discussed for electrochemical detection of different analytes. Preparation of hydrogel modified electrodes and state-of-the-art sensing mechanisms have been briefly emphasized. Concluding remarks and future prospects regarding fabrication of hydrogel based smart electronics have been provided at the end. (C) 2019 Elsevier B.V. All rights reserved
Performance enhancement by optimizing the reformer for an internal reforming methanol fuel cell
No full textInternal reforming methanol fuel cell (IRMFC) has potential applications in portable or stationary power supply system, but currently performance of the IRMFC is limited by the low hydrogen production of its reformer. In order to produce more hydrogen with less volume, in this paper a single channel serpentine packed bed reformer was designed, and its bed size was optimized by experiment and numerical simulation to enhance heat transfer and increase catalyst utilization. It was found that with the bed diameter from 5.8 mm down to 3.8 mm, the reformer temperature distribution was more uniform but the bed pressure drop increased a lot. Considering performance and pressure drop, the reformer of 5 mm was optimal, per milliliters of which could supply 9.8 mL/min hydrogen at 453 K, almost twice as much as that by A. Mendes et al with one-third of their catalyst loading. The reformer was quite stable, and less than 10% decline in methanol conversion was observed during the 100 hours period at 473 K. When incorporated into an IRMFC single cell, power density of the single cell reached 0.45-0.55 W/cm(2) at 453-473 K under CH3OH solution and air feed, the highest in existing reports. The main drawback has to do with low stability of the IRMFC single cell at high current density
Chemical Bath Deposition of Co-Doped TiO2 Electron Transport Layer for Hysteresis-Suppressed High-Efficiency Planar Perovskite Solar Cells
No full textPlanar hybrid perovskite solar cells (PSCs) attract great attention due to their obvious advantages of low-temperature processing with a high power conversion efficiency (PCE) up to 23.32%. Here, Co-doped TiO2 (Co-TiO2) deposited by a straightforward low-temperature chemical bath deposition (CBD) method is explored. Using Co-TiO2 as an electron transport layer (ETL) for the planar PSCs, the effects of doping on TiO2 morphology, electronic properties, and solar cell performance are investigated. The PCE increases to 19.10% when the Co doping concentration is optimized at 5 mol%, an increase of 17.40% compared with that using the pristine TiO2. Meanwhile, the notorious J-V hysteresis is suppressed to a greater extent. Considering that the low-temperature CBD is comparable with continuous roll-to-roll processing, it makes the process and the Co-TiO2 ETL potential candidates for low-cost commercialization
