Proposal for Improving the Durability of Carbon Material for Phosphoric Acid Fuel Cells (PAFC) by Revealing the Corrosion Factors

Kiho, Mariko; Matsunaga, Kotetsu; Morikawa, Shigeru; Katoh, Osamu

doi:10.5796/electrochemistry.70.104

Cited by 6 publications

(2 citation statements)

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“…Besides the coarsening of Pt, the corrosion of catalyst supports may be another critical issue for cell durability under certain operating conditions. Unlike the severe corrosion occurring in phosphoric acid fuel cells, which operate at about 200°C, 5 the corrosion of the commonly used carbon supports ͑e.g., Vulcan-XC72͒ is considered negligible in PEMFCs because of a significantly lower operating temperature, especially under a normal oper-ating potential ͑Ͻ0.8 V͒. 6 However, short-term potential excursions of cathode electrodes to more than 1.2 V may occur during the start-up and shutdown of fuel cells due to a so-called "reverse-current" mechanism.…”

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confidence: 99%

Durability Study on SWNT/Nanofiber Buckypaper Catalyst Support for PEMFCs

Zhu¹,

Zheng²,

Liang³

et al. 2009

J. Electrochem. Soc.

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Due to their unique microstructure, buckypaper-supported platinum ͑Pt͒ catalysts derived from carbon nanotube and carbon nanofiber have demonstrated a high Pt utilization in proton exchange membrane fuel cells ͑PEMFCs͒. ͓SWNT means singlewalled carbon nanotube.͔ The durability of a buckypaper-supported Pt catalyst was investigated using an accelerated degradation test ͑ADT͒ in a mimic cathode environment of PEMFC. Compared to commercial carbon black-supported Pt, Pt/buckypaper showed a better catalyst durability after holding at 1.2 V for 400 h; specifically, almost 80% of the Pt electrochemical surface area was lost for Pt/carbon black, with only a 43% loss for Pt/buckypaper. Transmission electron microscopy and cyclic voltammetry were used to study the Pt degradation mechanism. It was concluded that Pt coarsening and Pt detachment from buckypaper support due to carbon corrosion make the major contribution to the Pt surface area loss under this condition. The Pt loss via detachment from supports after the ADT was calculated as 18% in Pt/buckypaper, while the Pt loss was 69% in Pt/C. It is supposedly due to the higher corrosion resistance of buckypaper because of its high graphitization degree, which is indicated by a slower formation rate of surface oxides in buckypaper than in carbon black. Further durability improvement of the Pt/buckypaper is expected by improving the dispersion of Pt on the buckypaper to reduce Pt sintering.Proton exchange membrane fuel cell ͑PEMFC͒ technology has been extensively developed during the last decade and is rapidly approaching commercialization. High production cost, especially the catalyst cost due to the high price of platinum, is considered as one of the most important issues to hinder widespread application of PEMFCs. The state-of-the-art Pt utilization in a cell is 0.6 g Pt/kW with a Pt loading of 0.45 mg Pt/cm 2 , which is planned to be reduced to 0.3 g Pt/kW with a Pt loading of 0.2 mg Pt/cm 2 in a stack by 2015 to meet the requirements for transportation applications, according to the US Department of Energy's target. 1 Aside from cost, the durability of PEMFCs has been recognized recently as another critical issue for commercializing PEMFCs because 5000 h of cell operation is required for automotive applications and 40,000 h for stationary applications. Activity loss of the catalysts is believed to make a major contribution to the performance degradation of PEMFCs. 2 Conventional PEMFC catalysts are typically composed of platinum nanoparticles ranging in size from 2 to 3 nm dispersed on high surface area carbon materials, such as carbon black, to maximize the specific surface area of Pt. 3 The coarsening of Pt nanoparticles during cell operation is inherently driven by the reduction of surface energy resulting in a decrease of the electrochemical surface area ͑ECSA͒ of Pt. The catalytic activity of Pt toward the oxygen reduction reaction ͑ORR͒ decreases accordingly, leading to performance degradation of PEMFCs. The mechanisms of Ostwald ripening via a Pt dissolution and...

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Durability Study on SWNT/Nanofiber Buckypaper Catalyst Support for PEMFCs

Zhu¹,

Zheng²,

Liang³

et al. 2009

J. Electrochem. Soc.

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“…There has been considerable interest in developing well dispersed platinum nanoparticles on carbon due to their applications in fuel cells, catalytic converters and catalytic burners. [1][2][3][4][5] There are excellent reviews in the literature on this topic. [6][7][8] Carbonsupported platinum catalysts are usually synthesized by one of a few methods: (a) impregnation of an activated carbon support with a platinum salt precursor solution such as chloroplatinic acid, (b) adsorption of platinum oxide, platinum metal or colloids on the carbon surface 9,10 or (c) by ion exchange at the surface with a platinum amine complex.…”

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confidence: 99%