1,720,974 research outputs found
Recent Developments of Polymer Electrolyte Membrane Fuel Cell Design
No full textPEMFC has high potential for future development due to its high energy density, eco-friendliness, and high energy effi-ciency. When it becomes small, light and flexible, it can be competitive as an energy source for portable devices or flexible electronic devices. However, the use of hard and heavy materials for structural rigidity and uniform contact pressure trans-mission has become an obstacle to reducing the weight and flexibility of PEMFCs. This review intends to provide an exam-ple of the application of a new structure and material for lightweight and flexibility. As a lightweight PEMFC, a tubular design is presented and structural advantages through numerical modeling are explained. Manufacturing methods to realize the structural advantages and possibilities of tubular PEMFCs are discussed. In addition, the materials and manufacturing processes used to fabricate lightweight and flexible PEMFCs are described and factors affecting performance are analyzed. Strategies and structural improvements of light and flexible movements are discussed according to the component parts. © 2023, Korean Electrochemical Society. All rights reserved.11Nsciescopu
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
Maximizing the Active Site Densities of Single-Atomic Fe-N-C Electrocatalysts for High-Performance Anion Membrane Fuel Cells
No full textIron- and nitrogen-doped carbon (Fe-N-C) catalysts have received significant attention owing to their high oxygen reduction reaction (ORR) activities, which are comparable to those of state-of-the-art Pt/C catalysts. This high ORR activity originates from the atomically dispersed Fe coordinated with the nitrogen atom (Fe-N-x) active site. Increasing the Fe-N-x active site density can enhance the ORR activity. In this study, we suggest a facile and effective method for maximizing the active site densities using a simple ZnCl2 activation method. ZnCl2 activation was applied to the metal organic framework-derived Fe-N-C catalyst that exhibits superior ORR activity compared to Pt/C and a recently reported nonprecious metal catalyst. Through various electrochemical analyses, we confirmed that this activity originates from the effectively increased active site density. The anion-exchange membrane fuel cell (AEMFC) performance was measured to confirm practical applicability, and we obtained a significantly high performance of 1076 mA cm(-2) at 0.6 V, which is significantly higher than the currently reported performance of carbon-based Fe-N-C AEMFC cathode catalysts. We demonstrate the potential of our strategy for applications in various carbon-based materials that can be used for the development of high-efficiency electrochemical energy devices.11Nsciescopu
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
A hierarchical cathode catalyst layer architecture for improving the performance of direct methanol fuel cell
No full textWe report the fabrication of a hierarchical cathode catalyst layer (CL) for application in direct methanol fuel cells (DMFCs). The hierarchical CL, comprised of Pt black as the inner layer and Pt/C as the outer layer, has appropriate structural properties for DMFC cathode. The inner CL with compact structure decreases the CL thickness and prevent Pt sites from methanol contamination, and the cathode outer CL with porous structure increase the electrochemical active surface area. Consequently, the hierarchical cathode CL is able to offset the adverse effect of methanol crossover on the cathode performance by enhancing the Pt catalyst utilization for oxygen reduction reactions (ORR). Therefore, the newly developed membrane electrode assembly (MEA) can maintain the high ORR activity of the cathode catalysts despite the methanol crossover. At a high methanol concentration (3 M), it shows high maximum power density (0.156 W cm−2) despite only 1.0 mg cm−2 of Pt in the cathode CL. © 2017 Elsevier B.V1231sciescopu
Bi-modified Pt supported on carbon black as electro-oxidation catalyst for 300 W formic acid fuel cell stack
Full text link© 2019 Elsevier B.V. Formic acid is a chemical with a simple molecular structure containing hydrogen. This liquid at room temperature is easy to handle and has a low toxicity, and is thus in the spotlight as a fuel. In particular, formic acid is an excellent fuel candidate because it can be operated at low temperatures when applied as a fuel in fuel cells with a high theoretical open-circuit voltage (1.48 V). However, it has a drawback in that the electrode catalyst is deactivated due to the generation of CO intermediates when formic acid is oxidized during cell operation. Therefore, to prevent this, an irreversibly adsorbed Bi on Pt catalyst is applied to a direct formic acid fuel cell (DFAFC)anode because it is easy to synthesize and economical. Physical analyses such as transmission electron microscopy (TEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA)were conducted, and electrochemical evaluations were performed through half-cell and single-cell level tests. The results revealed that the formic acid oxidation reaction activity of the Bi-modified Pt/C was 13 times higher than that of the conventional catalyst at 0.58 V. Further, a DFAFC stack was fabricated using the Bi-modified Pt/C, which yielded a power of 300 W. These results suggest that a simple synthesis method can be applied to fabricating industrially available DFAFC stacks11sciescopu
Boosting electrochemical stability of ultralow-Pt nanoparticle with Matryoshka-like structure in polymer electrolyte membrane fuel cells
No full text© 2019 Elsevier B.V. Electrochemical catalysts with a core-shell structure have received much attention because of their enhanced efficiency and activity. Among them, those with a CuPd alloy core exhibit better activity than the ones with a single metal Pd core, which is known to be an excellent core-material. However, the superior performance of previously reported Pt catalysts with CuPd core has only been observed in half-cells, and was not reflected or even expanded to single-cells. We report catalysts having a Matryoshka-like structure with a Pt outer-layer, Cu interlayer, and Pd core for oxygen reduction reaction. This catalyst has 3.4 times higher Pt mass activity than the commercial Pt/C in half-cells, and also performs better in single-cells at only 0.056 mgPt cm−2. Particularly, the stability of this catalyst satisfies the 2020 DOE target, and electrochemical surface area loss during the stability test is only 40 % for this catalyst, while that of Pt/C is 80 %11sci
Achieving breakthrough performance caused by optimized metal foam flow field in fuel cells
Full text link© 2019 Hydrogen Energy Publications LLCEnhanced mass transport in polymer electrolyte membrane fuel cells (PEMFCs) is required for achieving high performance because concentration losses dominate cell performance. In particular, the flow field is crucial for mass transport. Recently, metal foam has been proposed as an alternative flow field owing to its three-dimensional pores, high porosity, and enhanced electrical conductivity. Here, we inspect the microstructure of various copper foams and investigate its effect as a flow field on PEMFCs. The PEMFCs with the optimized foam flow field deliver the highest performance reported to date. A large contact area and small ribs of the optimized foam flow field are advantageous for mass transfer and ohmic resistance. In addition, the internally generated pressure increases the partial pressure of the reactant, which leads to increased performance. This foam flow field has a significant potential for achieving high cell performance by enhancing the electrochemical reaction of the catalyst11sciescopu
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
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