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Research Paper

Comparison of Performance Losses Between Ultrasonic and Thermal Bonding of Membrane Electrode Assemblies in Proton Exchange Membrane Fuel Cells

[+] Author and Article Information
Casey Hoffman

Center for Automation Technologies and Systems,
Rensselaer Polytechnic Institute,
110 8th Street, Troy, NY 12180

1Corresponding author.

Contributed by Advanced Energy Systems Division of ASME for publication in the Journal of Fuel Cell Science and Technology. Manuscript received September 16, 2012; final manuscript received April 20, 2013; published online June 17, 2013. Assoc. Editor: Jacob Brouwer.

J. Fuel Cell Sci. Technol 10(4), 041004 (Jun 17, 2013) (10 pages) Paper No: FC-12-1095; doi: 10.1115/1.4024567 History: Received September 16, 2012; Revised April 20, 2013

Ultrasonic bonding of low-temperature PEM membrane electrode assembly (MEA) components together has been shown previously to cut both cycle time and energy input of that manufacturing step by over an order of magnitude as compared to the industry standard of thermal pressing. This paper compares performance between ultrasonically and thermally bonded low-temperature MEAs and characterizes the performance losses from the new bonding process. A randomized, full factorial experiment was designed and conducted to examine performance of MEAs with 10 cm2 active area while varying three factors: bonding method (ultrasonically and thermally pressed using previously optimized bonding parameters), membrane condition (dry and conditioned Nafion® 115), and electrode catalyst loading (0.16 and 0.33 mg Pt/cm2). Ultrasonic MEAs performed as well as their thermal MEAs across all tested current densities with pure oxygen supplied to the cathode. However, thermal MEAs outperformed ultrasonic MEAs at current densities above 0.4 A/cm2 with air supplied to the cathode. Impedance spectroscopy, cyclic voltammetry, and flow sensitivity analyses were used to characterize the performance losses of the ultrasonic MEAs. The data suggest the presence of oxygen diffusion losses above 0.4 A/cm2 when air was supplied to the cathode. Ultrasonic MEAs were three times more sensitive to changes in air flow rate on the cathode than the thermally MEAs. Increasing the platinum catalyst loading from 0.16 to 0.33 mg Pt/cm2 resulted in a performance enhancement of approximately 20 mV and 65% greater electrochemical surface area. Understanding the effect of ultrasonic bonding on various performance losses will help optimize the MEA bonding process. Analysis of specific losses present for ultrasonic MEAs may also provide insight into the design of MEA components for ultrasonic bonding.

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Figures

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Fig. 1

(a) Schematic of standard five-layer PEMFC MEA architecture and (b) dimensioned (cm) drawing of low-temperature MEA

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Fig. 2

(a) Labeled component diagram of ultrasonic bonding system and (b) actual system used for research

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Fig. 3

Schematic of the MEA setup prior to ultrasonic bonding

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Fig. 4

(a) 400 kN hot press used to bond MEAs and (b) schematic of MEA in press prior to thermal sealing

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Fig. 5

Cell testing hardware

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Fig. 6

MEA polarization curves for optimized ultrasonic and thermal MEAs using conditioned membrane, high-loaded electrodes (0.36 mg Pt/cm2), 2.0/2.0 stoich, and atmospheric pressure

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Fig. 7

Impedance scan data at 0.6 A/cm2 (semicircular shape) for an ultrasonically bonded MEA with high electrode loading and conditioned membrane

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Fig. 8

IR-corrected plot showing performance losses at high current densities of an ultrasonically bonded MEA consisting of conditioned membrane and high catalyst-loaded electrode tested with 2.0/2.0 stoich at 1 atm pressure

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Fig. 9

CV scan of ultrasonically bonded MEA (black) with thermal pressed MEA data (gray) overlaid

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