Effects of Freezing and Thawing on the Structures of Porous Gas Diffusion Media

2007 ◽  
Author(s):  
Joaquin A. Pelaez ◽  
Satish G. Kandlikar
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Active Surface ◽  
Membrane Electrode Assembly ◽  
Gas Diffusion ◽  
Membrane Electrode ◽  
Active Surface Area ◽  
Freezing And Thawing ◽  
Diffusion Media ◽  
Cell Components

Fuel cells are a very promising technology for transportation applications in the future. Many companies are performing research in order to make the implementation of fuel cell-powered vehicles more feasible. One issue that needs to be addressed is the fact that fuel cell vehicles will be used in sub-freezing climates. Vehicles undergo frequent shut down and startup events, and as such, freezing and thawing effects on fuel cell components become important when the vehicle is stored overnight in cold climates. When shut off, fuel cells will maintain water in the membrane electrode assembly (MEA) and gas diffusion media unless certain purging protocols are adhered to. When the cell is subjected to sub-freezing temperatures, the water remaining in these media will freeze. This freezing could have a detrimental impact on the pore structure, fiber integrity, and binder effectiveness in the GDL, thereby decreasing the electrochemical active surface area of the electrolytes and hurting the overall performance of the cell. This paper details the prior research in the area of freezing and thawing effects in these media and also details current research on the degradation of the GDL specifically.

A Feasibility Study of Ribbon Architecture for PEM Fuel Cells

2010 ◽  
Vol 7 (5) ◽  
Author(s):  
Daniel F. Walczyk ◽  
Jaskaran S. Sangra
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
High Volume ◽  
Pem Fuel Cells ◽  
Gas Diffusion ◽  
Open Circuit ◽  
Membrane Electrode ◽  
Fixture Design ◽  
Design Development ◽  
Test Fixture

The feasibility of an alternative fuel cell architecture, called a ribbon membrane electrode assembly (MEA), is demonstrated for low-temperature polymer electrolyte membrane (PEM) fuel cells used in portable power applications by comparing it to a traditional bipolar “stack” architecture. A ribbon MEA consists of adjacent PEM cells sharing a common gas diffusion layer to allow for lateral electrical current flow and an integral gas-tight, conductive interconnect/seal, where adjacent cells meet to prevent reactant gas leakage. The resulting lateral arrangement of MEAs can be used to supply all MEAs simultaneously instead of individual bipolar plates with flow fields for a stack. A pair of two-cell ribbon MEAs, with and without an interconnect/seal, were designed, prototyped, and sealed by thermal pressing. The MEAs were clamped in a two-piece box fixture to provide reactant gases on the anode and cathode sides, hooked to a fuel cell (FC) test stand and yielded an open circuit voltage (OCV) of 1.43 V with an interconnect/seal and 0.6 V without. A two-cell bipolar stack PEMFC with identical MEA specifications had an OCV of 1.86 V. Polarization curves for the ribbon MEA with interconnect/seal showed the sensitivity of performance to clamping pressure and positioning of the copper current collectors. The ribbon MEA polarization curve was also shifted downward by 0.42 V as compared with that of the traditional stack, and suspected causes (e.g., gas leaking) are attributable to the nonoptimal test fixture design. Hence, the ribbon MEA architecture is shown to be feasible. Future work suggested includes improvements to the test fixture design, development of automated manufacturing capabilities for high volume production, and demonstration of a multicell (>2) ribbon MEA PEMFC design.

Fuel Cell-Based MEMS Power Source

2008 ◽  
Author(s):  
Saeed Moghaddam ◽  
Eakkachai Pengwang ◽  
Kevin Lin ◽  
Rich Masel ◽  
Mark Shannon
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Hydrogen Generation ◽  
Control Mechanism ◽  
Membrane Electrode Assembly ◽  
High Energy ◽  
High Energy Density ◽  
Membrane Electrode ◽  
Mems Devices ◽  
Power Sources

The increasing demand for high energy density power sources driven by advancements in portable electronics and MEMS devices has generated significant interest in development of micro fuel cells. One of the major challenges in development of hydrogen micro fuel cells is the fabrication and integration of auxiliary systems for generation and delivery of fuel to the membrane electrode assembly (MEA). In this paper, we report the development of a millimeter-scale (3×3×1 mm3) micro fuel cell with on-board fuel and control system. Hydrogen is generated in the device through reaction between water and a metal hydride. The device incorporates a new control mechanism for hydrogen generation that occupies only 50 nL volume (less than 0.5% of the total device volume). More importantly, the control mechanism is self-regulating and does not consume any power, enabling the micro fuel cell to operate passively, similar to a battery.

Impedance-based Performance Analysis of Micropatterned Polymer Electrolyte Membrane Fuel Cells

2021 ◽  
pp. 1-33
Author(s):  
Morio Tomizawa ◽  
Keisuke Nagato ◽  
Kohei Nagai ◽  
Akihisa Tanaka ◽  
Marcel Heinzmann ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Polymer Electrolyte ◽  
Electrochemical Impedance ◽  
Catalyst Layer ◽  
Membrane Electrode Assembly ◽  
Gas Diffusion ◽  
Reduction Reaction ◽  
Proton Exchange ◽  
Operating Conditions ◽  
Membrane Electrode

Abstract Micropatterns applied to proton exchange membranes can improve the performance of polymer electrolyte fuel cells; however, the mechanism underlying this improvement is yet to be clarified. In this study, a patterned membrane electrode assembly (MEA) was compared with a flat one using electrochemical impedance spectroscopy and distribution of relaxation time analysis. The micropattern positively affects the oxygen reduction reaction by increasing the reaction area. However, simultaneously, the pattern negatively affects the gas diffusion because it lengthens the average oxygen transport path through the catalyst layer. In addition, the patterned MEA is more vulnerable to flooding, but performs better than the flat MEA in low-humidity conditions. Therefore, the composition, geometry, and operating conditions of the micropatterned MEA should be comprehensively optimized to achieve optimal performance.

A Novel Structure of Membrane Electrode Assembly for DMFC

2009 ◽  
Vol 60-61 ◽  
pp. 339-342
Author(s):  
Chun Guang Suo ◽  
Xiao Wei Liu ◽  
Xi Lian Wang
Keyword(s):  
Fuel Cell ◽  
Direct Methanol Fuel Cell ◽  
Catalyst Layer ◽  
Membrane Electrode Assembly ◽  
Gas Diffusion ◽  
Cathode Side ◽  
Membrane Electrode ◽  
Anode Side ◽  
Direct Methanol ◽  
Methanol Fuel Cell

Membrane electrode assembly (MEA) is the key component of direct methanol fuel cell (DMFC), the structure and its preparation methods may bring great effects on the cell performances. Due to the requirement of the high performance of the MEA for the micro direct methanol fuel cell (DMFC), we provide a novel double-catalyst layer MEA using CCM-GDE (Catalyst Coated Membrane，CCM；Gas Diffusion Electrode，GDE) fabrication method. The double-catalyst layer is formed with an inner catalyst layer (in anode side: PtRu black as catalyst, in cathode side: Pt black as catalyst) and an outer catalyst layer (in anode side: PtRu/C as catalyst, in cathode side: Pt/C as catalyst). The fabrication procedures are important to the new structured MEA, thus three kinds of fabrication methods are studied, including CCM-GDE, GDE-Membrane and CCM-GDL methods. It was found that the CCM-GDE technology may enhance the contact properties between the catalyst and PEM, and increase the electrode reaction areas, resulted in increasing the performance of the DMFC.

scholarly journals Structures of Membrane Electrode Assembly Catalyst Layers for Proton Exchange Membrane Fuel Cells

2012 ◽  
Vol 5 (1) ◽  
pp. 28-38 ◽  
Author(s):  
Tzyy-Lung Leon Yu ◽  
Hsiu-Li Lin ◽  
Po-Hao Su ◽  
Guan-Wen Wang
Keyword(s):  
Fuel Cells ◽  
Proton Exchange Membrane ◽  
Membrane Electrode Assembly ◽  
Gas Diffusion ◽  
Proton Exchange ◽  
Membrane Electrode ◽  
Catalyst Layers ◽  
Black Layer ◽  
Exchange Membrane ◽  
Pt Black

In this paper, we modify the conventional 5-layer membrane electrode assembly (MEA, in which a proton exchange membrane (PEM) is located at its center, two Pt-C-40 (Pt on carbon powder support, Pt content 40 wt.%) catalyst layers (CLs) are located on the surfaces of the both sides of the PEM and two gas diffusion layers (GDLs) are attached next on the outer surfaces of two Pt-C-40 layers) and propose 7-layer and 9-layer MEAs by coating thin Pt-black CLs at the interfaces between the Pt-C-40 layer and the GDL and between the PEM and the Pt-C-40 layer and reducing the Pt-C-40 loading. The reduced Pt loading quantity of the Pt-C-40 layer is equal to the increased Pt loading quantity of the Pt-black layer, thus the total amount of Pt loadings in the unmodified conventional MEA and the modified MEAs are at a fixed Pt loading quantity. These modified MEAs may complicate the manufacture process. The main advantage of these 7- and 9-layer MEAs is the thinner CL thickness and thus lower CL proton transport resistance. Because of the thin Pt-black layer thickness in MEA, we avoid agglomeration of the Pt-black particles and maintain high Pt catalytic activity. We show these new CL structure MEAs have better fuel cells performance than the conventional 5-layer MEA.

Gas diffusion layer/flow-field unified membrane-electrode assembly in fuel cell using graphene foam

2019 ◽  
Vol 323 ◽  
pp. 134808 ◽  
Author(s):  
Ji Eun Park ◽  
Jongkoo Lim ◽  
Myung Su Lim ◽  
Sungjun Kim ◽  
Ok-Hee Kim ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Flow Field ◽  
Diffusion Layer ◽  
Gas Diffusion Layer ◽  
Membrane Electrode Assembly ◽  
Gas Diffusion ◽  
Membrane Electrode ◽  
Graphene Foam ◽  
Layer Flow

scholarly journals Patterned Membranes for Proton Exchange Membrane Fuel Cells Working at Low Humidity

Polymers ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 1976
Author(s):  
Oliver Fernihough ◽  
Holly Cheshire ◽  
Jean-Michel Romano ◽  
Ahmed Ibrahim ◽  
Ahmad El-Kharouf ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Relative Humidity ◽  
Proton Exchange Membrane ◽  
Active Surface ◽  
Proton Exchange ◽  
Cathode Side ◽  
Membrane Electrode ◽  
Active Surface Area ◽  
Power Performance ◽  
Exchange Membrane

High performing proton exchange membrane fuel cells (PEMFCs) that can operate at low relative humidity is a continuing technical challenge for PEMFC developers. In this work, micro-patterned membranes are demonstrated at the cathode side by solution casting techniques using stainless steel moulds with laser-imposed periodic surface structures (LIPSS). Three types of patterns, lotus, lines, and sharklet, are investigated for their influence on the PEMFC power performance at varying humidity conditions. The experimental results show that the cathode electrolyte pattern, in all cases, enhances the fuel cell power performance at 100% relative humidity (RH). However, only the sharklet pattern exhibits a significant improvement at 25% RH, where a peak power density of 450 mW cm−2 is recorded compared with 150 mW cm−2 of the conventional flat membrane. The improvements are explored based on high-frequency resistance, electrochemically active surface area (ECSA), and hydrogen crossover by in situ membrane electrode assembly (MEA) testing.

Effect of Bolts Locking Sequence on Flow-Channel Plate in Micro-PEMFC

2008 ◽  
Author(s):  
Chi-Hui Chien ◽  
Shih-Chun Li ◽  
Wei-Tsung Hsu ◽  
Chih-Wei Lin
Keyword(s):  
Fuel Cell ◽  
Three Dimensional ◽  
Deformation Mode ◽  
Pem Fuel Cell ◽  
Membrane Electrode Assembly ◽  
Gas Diffusion ◽  
Flow Channel ◽  
Membrane Electrode ◽  
Cell Assembly ◽  
Channel Plate

The design and method of cell assembly play important roles in assessing the performance of PEM fuel cell. The cell assembly will affect the contact behavior between the bipolar plates, flow-channel plates, gas diffusion layers (GDLs) and membrane electrode assembly (MEA). From the past studies, it is noted that the flow-channel plates in the cell will be deformed while the cell was assembled by locking with bolts. This phenomenon may lead to leakage of fuels, high contact resistance and malfunctioning of the cells. The main aim of this research is to study the variation of the deformation mode of the flow-channel plat in a micro-PEM fuel cell assembly subjected to different bolts locking sequences. The commercial FEM package, ANSYS, was adopted to model the three-dimensional single micro-PEMFC FEM model and the numerical simulation analyses were performed. The effect of the bolts locking sequence on the deformations of flow-channel plate in the micro-PEMFC was presented.

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