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Research Papers

In Situ and Ex Situ Studies on the Degradation of Pd/C Catalyst for Proton Exchange Membrane Fuel Cells

[+] Author and Article Information
Yongfu Tang

Hebei Key Laboratory of Applied Chemistry,
College of Environmental and Chemical Engineering,
Yanshan University,
Qinhuangdao, Hebei 066004, China
e-mail: tangyongfu@ysu.edu.cn

Shichun Mu

State Key Laboratory of Advanced Technology
for Materials Synthesis and Processing,
Wuhan University of Technology,
Wuhan 430070, China

Shengxue Yu, Yufeng Zhao, Hongchao Wang, Faming Gao

Hebei Key Laboratory of Applied Chemistry,
College of Environmental and Chemical Engineering,
Yanshan University,
Qinhuangdao, Hebei 066004, China

1Corresponding author.

Contributed by the Advanced Energy Systems Division of ASME for publication in the JOURNAL OF FUEL CELL SCIENCE AND TECHNOLOGY. Manuscript received August 30, 2013; final manuscript received April 12, 2014; published online June 10, 2014. Assoc. Editor: Umberto Desideri.

J. Fuel Cell Sci. Technol 11(5), 051004 (Jun 10, 2014) (7 pages) Paper No: FC-13-1079; doi: 10.1115/1.4027708 History: Received August 30, 2013; Revised April 12, 2014

To investigate the degradation mechanism of the as-prepared Pd/C catalyst, in situ and ex situ accelerated stress tests were carried out via potential cycling. Durability tests of the single cells with Pd/C catalysts were performed through an interval constant current density mode. Electrochemical impedance spectroscopy (EIS) was applied to measure the impedance of the single cell during degradation tests. Results indicate that the degradation of Pd/C catalyst may be attributed to the phase transition of absorbed α-phase PdH to β-phase PdH, the dissolution of Pd metal, and the size increase of Pd nanoparticles. Moreover, the degradation of single cell may be predominantly ascribed to the degradation of catalyst, the deterioration of contact between electronic/ionic conductors, as well as the flooding of gas diffusion channels.

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Figures

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Fig. 1

(a) CV curves of the Pd/C catalyst at different potential cycles during the AST test with scan rate of 50 mV s−1 and (b) ORR curves of Pd/C catalyst before and after 200 potential cycles with scan rate of 5 mV s−1 and rotation speed of 1600 rpm. The electrolytes are the in N2-saturated and O2-saturated 0.5 M H2SO4 solutions, respectively.

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Fig. 2

Typical TEM images of the Pd/C catalyst before (a) and after (b) 200 CV potential cycles

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Fig. 3

CV curves of the MEA with Pd/C catalyst after different potential cycles during the accelerated stress test. Potential scan rate: 20 mV s−1.

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Fig. 4

Performances of single cell with Pd/C catalyst after different potential cycles during the accelerated stress test at cell operating temperature of 80 °C. Anode: the commercial TKK 28.4 wt.% Pt/C with the Pt loading is 0.3 mg cm−2. Total metal loading of cathode: 0.5 mg cm−2. H2/O2 pressure: 0.2 MPa/0.2 MPa. Membrane: Nafion 212. Pure hydrogen and pure oxygen were put into the anode and the cathode with saturated humidification, respectively.

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Fig. 5

EISs of single cell with Pd/C catalyst after different potential cycles at the current density of 100 mA cm−2 (a), 200 mA cm−2 (b), and 500 mA cm−2 (c) during the accelerated stress test. (d) The magnification of (a) (100 mA cm−2) at high frequency region.

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Fig. 6

Voltage of single cell with Pd/C catalyst operating at interval constant current mode at 80 °C. Anode: the commercial TKK 28.4 wt.% Pt/C with the Pt loading is 0.3 mg cm−2. Total metal loading of cathode: 0.5 mg cm−2. H2/O2 pressure: 0.2 MPa/0.2 MPa. Membrane: Nafion 212. Pure hydrogen and pure oxygen were put into the anode and the cathode with saturated humidification, respectively.

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Fig. 7

Performances of single cell at different discharging time during the durability test

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Fig. 8

EISs of single cell after different times at current densities of 100 mA cm−2 (a), 200 mA cm−2 (b), and 500 cm−2 (c) during durability test according to the performance measurements

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