1,721,045 research outputs found
Low-Cost and High-Performance Anion-Exchange Membrane Water Electrolysis Stack Using Non-Noble Metal-Based Materials
No full textWith increasing hydrogen demand, the development of a low-cost and high-performance anion-exchange membrane water electrolysis (AEMWE) stack is crucial. Here, two AEMWE models using all non-noble metal-based components were developed. Three components of the membrane electrode assembly─a porous transport layer (PTL), an oxygen evolution reaction (OER) catalyst, and a hydrogen evolution reaction (HER) catalyst─were examined to be substituted for a non-noble metal. The results revealed that stainless steel felt and carbon paper were the anode and cathode PTLs, respectively, exhibiting the highest and most durable performance. Additionally, nickel-iron (NiFe) was selected as the most applicable OER catalyst. Further, low-loading platinum and nickel-iron oxide (NiFeOx) were optimized as suitable HER catalysts. For a single cell, the resulting AEMWEs showed outstanding performance of 4633 and 1231 mA cm-2 at 2.1 V, with stable performance for 500 h. Further, they exhibited a higher performance relative to their cost than all noble metal AEMWEs. High performances were also observed for 5-layer stacks, in addition to stable durability and energy conversion efficiency. This work supports the commercialization of a low-cost, high-performance, and durable AEMWE stack. © 2023 American Chemical Society11Nsciescopu
Directly Coated Iridium Nickel Oxide on Porous‐Transport Layer as Anode for High‐Performance Proton‐Exchange Membrane Water Electrolyzers
No full textAbstract Developing a high‐performance anode design is important for a low‐cost proton‐exchange membrane water electrolyzer (PEMWE). In this study, an iridium nickel oxide directly coated anode (IrNiOx electrode) for high‐efficient PEMWE is reported. Five IrNiOx electrodes with different Ir‐to‐Ni ratios are developed using co‐electrodeposition. The resulting electrodes contain a thin IrNiOx layer on the carbon substrate. To develop the PEMWE incorporating IrNiOx electrode, the effect of fabrication methods, catalyst compositions, and porous transport layer are investigated. Consequently, the IrNiOx electrode prepared with 7:3 precursor solution (Ir0.5Ni0.5Ox) exhibits higher oxygen evolution reaction activity with a smaller overpotential than the electrode prepared with 10:0 precursor solution (IrOx) and the commercial IrO2. Furthermore, the performance of the PEMWE is higher with the Ir0.5Ni0.5Ox electrode than that with the sprayed electrode with commercial IrO2 nanoparticles. This enhancement is attributed to the high electrochemical surface area caused by introducing Ni in IrOx. Additionally, the performance of the directly coated Ir0.5Ni0.5Ox PEMWE is the highest reported in the literature
Origami-Based Flexible and Simple Tubular Polymer Electrolyte Membrane Fuel Cell Stack
No full textFlexible
energy devices are essential for future small and flexible
devices, and there are many challenges to create deformable energy
devices. In this study, we developed a lightweight and flexible passive
air-breathing polymer electrolyte membrane fuel cell (PEMFC) stack
with a flexible 3D structure using a straw-like tubular design. This
stack is lighter than a conventional PEMFC stack because it contains
a smaller number of components. By applying a conical design, the
device was easily assembled with the units connected in series using
banded-type connections (i.e., without clamps or fixing parts). Moreover,
for the first time, a conical reverse truss origami design was applied
to the tubular PEMFC, which enabled 3D movement and reduced the volume
of the PEMFC. The flexible tubular PEMFC is expected to be an energy
source for small devices and can be used to replace wires or external
fuel pipelines in devices that require mechanical movement
Effect of catalyst layer designs for high-performance and durable anion-exchange membrane water electrolysis
No full text© 2022 The Korean Society of Industrial and Engineering ChemistryDevelopment of anode design is crucial for highly efficient and durable anion-exchange membrane water electrolysis (AEMWE) as the kinetic of oxygen evolution reaction (OER) is sluggish. In this study, a macroporous catalyst layer (macroporous_CL) was proposed as an anode design for AEMWE to enhance the catalyst utilization. A macroporous_CL contains pores of two main size ranges: hundreds of nanometers and hundreds of micrometers. It is prepared using a spraying method to form nanometer-sized pores. The use of a stainless-steel (SUS) porous transport layer (PTL) as the substrate of the spraying method produces micrometer-sized macropores. In an investigation of the effects of the macroporous_CL and conventional catalyst layer (plain_CL) on AEMWE using two different kinds of oxygen evolution reaction (OER) catalysts, the macroporous_CL exhibited higher performance with lower ohmic and charge-transfer resistances compared to the plain_CL. This performance enhancement was attributed to the improved catalyst utilization and electron transport. Also, the macroporous_CL showed better durability compared to the plain_CL. Therefore, the macroporous_CL has been considered as an alternative anode design for AEMWE.N
High-performance and durable water electrolysis using a highly conductive and stable anion-exchange membrane
No full text© 2022 Hydrogen Energy Publications LLCThe commercialization of anion-exchange membrane water electrolysis (AEMWE) is crucial to produce low-cost and high-purity hydrogen. However, water electrolysis with an anion-exchange membrane (AEM) has limitations such as its low ionic conductivity and stability, leading to low performance and durability of AEMWE. In this study, we developed high-performance and stable AEMWE employing an AEM without aryl-ether backbone structure. To achieve high-performance and durable AEMWE, the effect of various parameters that is suitable for the adapted AEM was investigated. As a result, the AEM adapted in this work performed much better and was more durable than the conventional AEM (FAA-3). Moreover, it exhibited high efficiency under pure water feeding conditions. These results were attributed to high-efficient and durable AEM caused by its absence of aryl-ether backbone. This work suggests the potential use of polyphenylene structure as aryl-ether free backbone of AEM on AEMWE operated using alkaline solution and/or pure water.11Nsciescopu
Effect of iridium oxide as an additive on catalysts with different Pt contents in cell reversal conditions of polymer electrolyte membrane fuel cells
No full text© 2021 Hydrogen Energy Publications LLCCell reversal is observed when a current load is applied to the polymer electrolyte membrane fuel cell under fuel starvation conditions. Cell reversal causes severe corrosion (or oxidation) of the carbon support in the anode, which leads to a decrease in overall fuel cell performance. To suppress the corrosion reaction of carbon under cell reversal conditions and to increase the durability of fuel cells, studies on anode additives are being conducted. However, studies on the effect of additives on catalysts with different platinum contents have not been conducted. In this study, 20 wt%, 40 wt%, 60 wt% commercial Pt/C catalyst was applied to the anode, and 50 cycles of cell reversal were performed. Furthermore, the performance change with and without IrO2 as an additive was observed and its effect was assessed. Changes in the morphologies of the electrodes before and after cell reversal tests were also observed using a transmission electron microscope and a scanning electron microscope. The higher the platinum content of the catalyst, the more resistant to cell reversal. In addition, the addition of IrO2 to the anode effectively prevents performance degradation due to cell reversal.11Nsciescopu
Poly(carbazole)-based anion-conducting materials with high performance and durability for energy conversion devices
No full text© The Royal Society of Chemistry 2020. Anion conducting polymers (ACPs) are essential materials for alkaline electrochemical energy technology such as anion-exchange membrane fuel cells (AEMFCs) and water electrolysers (AEMWEs). The aforementioned polymers are promising alternatives for proton exchange membrane-based systems due to the possibility of using platinum group metal-free electrocatalysts. However, there are still no reliable ACPs possessing the desired performance and stability, which is a major challenge for developing alkaline energy systems. Herein, we highlight an anion-exchange membrane and ionomer based on quaternised poly-carbazole (QPC-TMA) with a rigid ether-free and curved backbone structure comprised of carbazole monomers. The developed ACP exhibits excellent ionic conductivity, as well as chemical and mechanical stability. Moreover, the AEMFC usingQPC-TMAshows excellent performance (1.61 W cm(-2)) compared with the other best-performing AEMFCs. In addition, the AEMWE usingQPC-TMAdemonstrates outstanding stability and state-of-the-art performance (3.5 A cm(-2)at 1.9 V), which is the first report of an AEMWE that outperforms the best-performing proton-exchange membrane water electrolysers11sciescopu
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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