Deterioration of granular activated carbon collected from post-ozonation upflow fluidized bed contactor—influence of particle diameter

Fukuhara, Tomoko; Yoshinaka, Masaharu; Katsu, Sachiko; Abe, Ikuo

doi:10.2166/aqua.2008.104

Journal of Water Supply: Research and Technology-Aqua

2008

DOI: 10.2166/aqua.2008.104

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Deterioration of granular activated carbon collected from post-ozonation upflow fluidized bed contactor—influence of particle diameter

Tomoko Fukuhara

Masaharu Yoshinaka

Sachiko Katsu³

et al.

Abstract: Raw mineral bauxites with and without thermal treatment were used as catalysts in a catalyzed ozonation process for the degradation of a typical taste and odour compound 2-Methylisoborneol (MIB). Compared with the sole ozonation or catalyst adsorption, raw mineral bauxite without further thermal treatment did not exhibit remarkable catalytic activity. But all bauxite catalysts with further thermal treatment exhibited some catalytic activity. Changing of the crystalline form during the thermal treatment played … Show more

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“…It is also known that activated carbon is degraded by O 3 used in the watertreatment process for drinking water production. 20,21 O 3 might be appropriate to oxidize the carbon surface of Pt/C without affecting the surface of the polymer electrolyte. The stability of Nafion, the most common polymer electrolyte for the PEFC, to the oxidation by O 3 is suggested by the facts that Nafion is used as an electrolyte in a water electrolysis cell for O 3 generation 22 and that the cell could be operated stably for 2500 h generating O 3 over 5 mg dm −3 in water.…”

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Carbon Surface Oxidation by Short-Term Ozone Treatment for Modeling Long-Term Degradation of Fuel Cell Cathodes

Maruyama¹,

Umemura²,

Inaba³

et al. 2009

J. Electrochem. Soc.

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In regard to degradation phenomena in a polymer electrolyte fuel cell ͑PEFC͒, there is little information on voltage loss due to the excess accumulation of liquid water blocking pores for the gas supply in the cathode ͑flooding͒ observed in a long-term operation over 5000-10,000 h. In this study, modeling of this degradation phenomenon was attempted using ozone treatment of the cathode catalyst layer ͑CL͒. The hydrophilicity of the layer was increased by the treatment, which was attributed to oxidation of the carbon surface of the catalyst ͑Pt-loaded carbon black, Pt/C͒ exposed to the gas phase in the CL. The flooding was observed at the PEFC with the cathode CL formed using 10 wt % Pt/C and treated with ozone for 10 h, and the extent of the flooding was enlarged by the ozone treatment of 15 h. The flooding was caused by the 5 h ozone treatment when the Pt content was 20 or 50 wt %. These results indicated that modeling of the long-term degradation was achieved by the short-term ozone treatment, and that the excessive hydrophilicity of the carbon surface of Pt/C was one of the highly potent candidates for causes of the degradation.Polymer electrolyte fuel cells ͑PEFCs͒ have recently been in practical use in power sources of electric vehicles and cogeneration systems for domestic electricity and heating, although the scale of PEFC usage is very limited. 1 Because the PEFC converts chemical energy to electricity by H 2 oxidation at the anode and O 2 reduction at the cathode in high efficiency with only water exhausted, 2-4 the substitution of conventional energy systems by the PEFC would help to improve the global environment. 5 In the next stage of the realization of the practical use of the PEFC, it is necessary to increase the number of the PEFC systems by gaining reliability and reducing the cost of the system. Durability of the PEFC closely relates to the reliability and the cost reduction. To obtain information about avoiding degradation of the PEFC and producing durable PEFCs, there have been an increased number of studies on the degradation mechanism at the components of the PEFC. 6 Nevertheless, several degradation phenomena occurring during a long-term operation have not clarified yet. One of those is the voltage loss at the cathode due to blocking of pathways for O 2 transfer by liquid water ͑flooding͒, which often begins to be observed for the operation over 5000-10,000 h in the state-of-the-art PEFC, 7 less than the PEFC-lifetime target of 40,000-90,000 h for the stationary PEFCs. Few studies have been reported so far on the mechanism of this degradation phenomenon and on the place causing the degradation.The O 2 transfer pathways are pores inside the cathode. They are faced with the surface of the catalyst particles consisting of Pt or Pt alloy supported on carbon black ͑hereafter called Pt/C͒ and the surface of the polymer electrolyte covering Pt/C in the catalyst layer ͑CL͒, and the surface of carbon and the fluorinated resins in the gas-diffusion layer. In the case of the PEFC degradation that give...

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confidence: 99%

Carbon Surface Oxidation by Short-Term Ozone Treatment for Modeling Long-Term Degradation of Fuel Cell Cathodes

Maruyama¹,

Umemura²,

Inaba³

et al. 2009

J. Electrochem. Soc.

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Deterioration of granular activated carbon collected from post-ozonation upflow fluidized bed contactor—influence of particle diameter

Cited by 1 publication

References 23 publications

Carbon Surface Oxidation by Short-Term Ozone Treatment for Modeling Long-Term Degradation of Fuel Cell Cathodes

Carbon Surface Oxidation by Short-Term Ozone Treatment for Modeling Long-Term Degradation of Fuel Cell Cathodes

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