1,721,315 research outputs found
Structural modification of electrode for anion exchange membrane fuel cell by controlling ionomer dispersion
No full textAn appropriate electrode microstructure design should be necessary to achieve high-performance anion exchange membrane fuel cells (AEMFCs). In general, the electrodes are fabricated from catalyst slurries which contain self-assembled agglomerates of catalyst particles with ionomer dispersed in a solvent. Therefore, solvent nature greatly affects the microstructure of the electrode, such as the pore structure and the formation of triple-phase boundaries for electrochemical reactions. Here, we investigate the influence of solvent on the microstructure of I2 ionomer-based electrode and its performance using three alcohol-based solvents (ethanol, 2-propanol, and 2-methyl-2-propanol [tBuOH)) with different dielectric constants and similar boiling points. Various physical and electrochemical characterization confirmed that the electrode pore structure changes significantly depending on the type of solvent while the electrochemically active surface area hardly changes. Furthermore, the efect of the three electrodes with different pore structures on AEMFC performance is observed for anode and cathode, respectively. It is demonstrated that the porous electrode with large pores is more advantageous in performance than a dense electrode at both the anode and the cathode for AEMFC. Consequently, the membrane electrode assembly with porous tBuOH-based electrodes exhibits more than 40% higher performance (1.32 W cm(-2)) than dense ethanol-based electrodes (0.94 W cm(-2)).11Nsciescopu
Fabrication of an Ionomer-Free Electrode Containing Vertically Aligned One-Dimensional Nanostructures for Alkaline Membrane Fuel Cells
No full textAn ionomer-free electrode containing vertically aligned one-dimensional nanostructures was designed and fabricated for anion exchange membrane fuel cells (AEMFCs) by hydrothermal and vapor deposition processes. The silver-coated zinc oxide (ZnO) nanorod arrays (diameter = ca. 100 nm) were directly aligned with the gas diffusion layer (GDL), and these one-dimensional structures of the electrode enhanced the mass transport of the reactants to the catalytic surface via its short diffusion pathway and ionomer-free nature. Applied as a cathode, the membrane electrode assembly (MEA) containing the vertically aligned gas diffusion electrode showed about 80% increased maximum power density than that of MEA containing a conventional electrode, which consisted of randomly dispersed carbon-supported nanoparticle catalysts and an ionomer. Moreover, the durability test revealed that the prepared ionomer-free catalyst layer was a more stable electrode than the conventional one. Also, water consumption and oxygen transport characteristics of AEMFC with the ionomer-free electrode at the cathode were intensively investigated by varying the electrode thickness and compositions. (C) 2021 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited.11Nsciescopu
Reduction of methanol crossover by thin cracked metal barriers at the interface between membrane and electrode in direct methanol fuel cells
No full textThis work reports the successful reduction in methanol crossover by creating a thin cracked metal barrier at the interface between a Nafion® membrane and an electrode in direct methanol fuel cells (DMFCs). The cracks are generated by simple mechanical stretching of a metal deposited Nafion® membrane as a result of the elastic mismatch between the two attached surfaces. The cracked metal barriers with varying strains (∼0.5 and ∼1.0) are investigated and successfully incorporated into the DMFC. Remarkably, the membrane electrode assembly with the thin metal crack exhibits comparable ohmic resistance as well as reduction of methanol crossover, which enhanced the device performance. © 2017 Elsevier B.V2
Atomization driven crystalline nanocarbon based single-atom catalysts for superior oxygen electroreduction
No full text© 2022 The AuthorsAtom-migration-trapping (AMT) is an effective and straightforward strategy for fabricating single-atom catalysts (SACs), but understanding the mechanism and effects of anchoring sites on AMT are formidable challenges. Here, we demonstrate that AMT phenomena occurs in crystalline porous nanocarbon, which allows development of highly efficient SACs via systematic investigation of atomization process and chemical state of active sites. An arc discharge-based bottom-up synthesis can generate an ideal porous nanocarbon with controllable nitrogen functionality, containing metal nanoparticles for AMT. Pre-formed N-functionalities in as-synthesized catalyst play important role in capturing single metal species, while additional ammonia treatment successfully modulates coordination geometry of active sites. The atomic cobalt catalyst exhibits superior oxygen reduction activity with remarkable power performance in single-cell experiments (752 mW cm−2), exceeding the reported Co-N atomic catalysts. Our findings provide not only new perspectives in AMT phenomena but also strategies to develop an efficient and practical SACs in energy conversion systems.11Nsciescopu
Interface engineering for high-performance direct methanol fuel cells using multiscale patterned membranes and guided metal cracked layers
No full textCapability to fabricate high-performance membrane electrode assemblies (MEAs) is a key to the commercialization of direct methanol fuel cells (DMFCs). This work reports an interface engineering method to introduce a multiscale patterned membrane and a guided metal cracked layer between the catalyst layer and the membrane by the creep-assisted sequential imprinting and simple stretching technique. The MEA with a multiscale patterned membrane, where the nanopatterns covered the whole surface even on the side surface of microstructures, showed improved performance owing to enhanced mass transport by the thinned electrode, effective utilization of the active sites, and increased Pt utilization. To obtain further performance enhancement, we incorporated a guided gold cracked layer into the MEA with the multiscale patterned membrane. The electrochemically inactive thin gold layer acted as a physical barrier for methanol crossover and the guided cracks provided multiple proton pathways. Our interface engineering utility resulted in an enhancement of the device performance by 42.3% compared with that of the reference
© 2017 Elsevier Ltd. All rights reserved1
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
Highly effective removal of cesium ion by a three-dimensional porous hydrogels embedded with potassium copper hexacyanoferrate nanoparticles
No full textHighly effective removal of Cs+ from aqueous solutions by the immobilization of potassium copper hexacyanoferrate in a cellulose-based hydrogel
No full text
High-performance fuel cell with stretched catalyst-coated membrane: One-step formation of cracked electrode
Full text linkWe have achieved performance enhancement of polymer electrolyte membrane fuel cell (PEMFC) though crack generation on its electrodes. It is the first attempt to enhance the performance of PEMFC by using cracks which are generally considered as defects. The pre-defined, cracked electrode was generated by stretching a catalyst-coated Nafion membrane. With the strain-stress property of the membrane that is unique in the aspect of plastic deformation, membrane electrolyte assembly (MEA) was successfully incorporated into the fuel cell. Cracked electrodes with the variation of strain were investigated and electrochemically evaluated. Remarkably, mechanical stretching of catalyst-coated Nafion membrane led to a decrease in membrane resistance and an improvement in mass transport, which resulted in enhanced device performance.19101sciescopu
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