Current Progress of Electrocatalyst R&amp;D in TKK

Tada, Tomoyuki; Yamamoto, Yumi; Matsutani, Koichi; Hayakawa, Katsuichiro; Namai, Tatsunori

doi:10.1149/1.2981857

Cited by 18 publications

(16 citation statements)

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“…Recently, similar observations were also made by Tada et al on Pt/SiO 2 . 53 Thus, we believe that such decrease of the kinetics of surface oxide formation might be a fingerprint of metal-oxide supported Pt nanoparticles (in this work, the addition of Vulcan XC72R rules out the ohmic drop effect).…”

Section: Oxygen Adsorption/desorptionmentioning

confidence: 70%

The role of the support in CO_adsmonolayer electrooxidation on Ptnanoparticles: Pt/WO_xvs.Pt/C

Micoud

Maillard

Bonnefont

et al. 2010

Phys. Chem. Chem. Phys.

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The electrocatalytic properties of home-made Pt nanoparticles supported onto WO(x) were determined for the electrooxidation of a CO(ads) monolayer and compared with that of a commercial Pt/C having the same Pt particle size. By combining electrochemical and spectroscopic techniques, we found that Pt/WO(x) nanoparticles exhibit a very high tolerance to CO at low electrode potentials (E = 0.1 V vs. RHE), which was never reported in the literature before. CO adsorption at E = 0.1 V vs. RHE on Pt/WO(x) yields CO(2) production as observed by Fourier-transform infrared spectroscopy (FTIR). When the gas bubbling in solution changes from CO to Ar, the current attenuates and the CO(2) production vanishes. This points towards a limited number of "active sites" and a slow step in the electrocatalytic process. When H(2) is used to purge the electrolyte from CO, a steep and continuous increase of the H(2) electrooxidation current is observed pointing towards continuous liberation of the Pt catalytic sites. The high tolerance to CO of Pt/WO(x) is discussed in terms of strong metal-support interaction (SMSI), which involves formation of a metal-oxide film partially covering the Pt nanoparticles (encapsulation) and creation of W-OH groups upon H(+) insertion at low electrode potentials.

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Section: Oxygen Adsorption/desorptionmentioning

confidence: 70%

The role of the support in CO_adsmonolayer electrooxidation on Ptnanoparticles: Pt/WO_xvs.Pt/C

Micoud

Maillard

Bonnefont

et al. 2010

Phys. Chem. Chem. Phys.

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“…Accelerated testing of carbon loss was evaluated using 25 cm 2 MEAs that were held at a high potential under a H 2 /N 2 condition. 21,22 In the experiments, Nafion 112 was used as a mem-brane electrolyte, and 50 wt % Ketjenblack carbon-supported Pt catalyst ͑Tanaka Kikinzoku Kogyo K.K.͒ was applied to a level of 0.5 mg Pt/cm 2 on each electrode. As it is difficult to directly determine the rate of the electrochemical oxidation of carbon from the measured current due to the simultaneous evolution of oxygen, the carbon-oxidation current was calculated from the CO 2 concentration in the exhaust gas and the total gas flow rate.…”

Section: Methodsmentioning

confidence: 99%

“…It is well known that the carbon materials are quickly oxidized at high potentials. [19][20][21] Often, the susceptibility to electrochemical oxidation is accurately evaluated by holding at open-circuit voltage ͑OCV͒. 22,23 A constant potential hold test at 1.2 V has been used as an accelerated test for resistance to carbon oxidation.…”

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confidence: 99%

Modeling and Investigation of Carbon Loss on the Cathode Electrode during PEMFC Operation

Takeuchi

Fuller

2010

J. Electrochem. Soc.

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Severe carbon loss phenomena, such as partial hydrogen starvation and start-up, have been investigated in previous works. Even for short times, these acute situations can be fatal, and some methods have been suggested to mitigate carbon oxidation and improve proton exchange membrane fuel cell ͑PEMFC͒ durability. By comparison, the rate of carbon loss is low during an ordinary PEMFC operation. Although less severe than for hydrogen starvation and start-up, the impact is still large enough so that the cell performance degrades markedly after a long-term operation. In this work, carbon loss during a PEMFC operation is investigated with a physical model. These results quantify the effects that cell voltage, activity for oxygen reduction, humidity, and temperature have on the rate of carbon loss. More rapid kinetics for oxygen reduction promotes carbon loss by lowering the solution potential at the fuel cell cathode.Carbon is used extensively as the support for catalysts in proton exchange membrane fuel cells ͑PEMFCs͒. Loss of carbon is a wellknown degradation phenomenon in PEMFC electrodes, and this electrochemical oxidation of carbon causes cell performance to decay. The relationship between carbon loss and cell performance was confirmed by Yu et al. 1 A reduction in carbon of only 5 wt % results in a large drop in cell voltage under a fuel cell operation at a constant current. Because Reiser et al. reported a "reverse current mechanism," 2 carbon losses under partial hydrogen starvation 3 and start-up 4 conditions have been discussed collectively as carbondegradation phenomena in PEMFCs, and the potentially fatal consequences have been noted. 5-12 Makharia et al. suggested that only 1 h under conditions of partial hydrogen starvation caused a loss of more than 5 wt % carbon. 13 Takeuchi and Fuller reported that under severe conditions, a large carbon loss ͑Ͼ1 wt %͒ was expected during the start-up of the fuel cell when air and hydrogen gases were exchanged in the fuel cell anode. 14 As the details of the reverse current mechanism have been elucidated, some methods to mitigate these effects for partial hydrogen starvation and start-up conditions have been proposed. Reducing the loading of a Pt catalyst on the fuel cell anode is an effective mitigation for both cases of carbon loss. 9,10,14,15 At start-up, careful control of the cell voltage also reduces carbon loss, and keeping the cell voltage low can prevent fatal damage for the fuel cell cathode. 14,16 These approaches help to improve the durability of PEMFC membrane electrode assemblies ͑MEAs͒ by eliminating the most severe conditions that cause fatal damage to fuel cell cathodes.Even if we can avoid these catastrophic situations mentioned above, low rates of carbon oxidation are still expected under an ordinary PEMFC operation, especially under high temperature conditions. Whereas a minimum operational life of 5000 h is required for transportation applications, 17 the rate of carbon loss may be 1-10 wt % per 1000 h, large enough to cause the decay of PEMFC perf...

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“…[18][19][20] For this reason, SnO 2 is one of the most promising carbon-free support materials, and many studies have been performed exploring the use of this material in PEFCs. [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] * Electrochemical Society Member.…”

mentioning

confidence: 99%

PEFC Electrocatalysts Supported on Nb-SnO₂for MEAs with High Activity and Durability: Part I. Application of Different Carbon Fillers

Nakazato

Kawachino

Noda

et al. 2018

J. Electrochem. Soc.

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Currently, carbon black is widely used as an electrocatalyst support for polymer electrolyte fuel cells (PEFCs). However, electrochemical oxidation leads to degradation of this material. In contrast, tin oxide (SnO 2 ) is electrochemically stable even under strongly acidic conditions, and relatively high electronic conductivity can be achieved by doping with niobium (Nb-SnO 2 ), compared with other metal oxides. In this study, Nb-SnO 2 is composited with various conductive carbon fillers, including vapor-grown carbon fibers (VGCF), carbon nanotubes (CNT), and graphitized carbon black (GCB), followed by platinum nanoparticle decoration. These nanocomposite electrocatalysts are incorporated into membrane electrode assemblies (MEAs) and tested under PEFC operational conditions. The resulting fuel cells achieve high initial I-V performance up to 0.742 V at 0.2 A cm −2 (80 • C), as well as excellent cycling durability. In particular, MEAs fabricated with Pt/Nb-SnO 2 /VGCF cathode electrocatalysts exhibit remarkable durability, with only a 12.1% drop in cell voltage at 0.2 A cm −2 over 60,000 start-stop cycles, and a 42.9% drop over 400,000 load potential cycles, corresponding to the lifetime of a fuel cell vehicle (FCV). Platinum-decorated metal oxide electrocatalysts can simultaneously realize high catalytic activity and extended durability, not only in ex-situ half-cell measurements, but also in full cell conditions.

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Current Progress of Electrocatalyst R&D in TKK

Cited by 18 publications

References 0 publications

The role of the support in CO_adsmonolayer electrooxidation on Ptnanoparticles: Pt/WO_xvs.Pt/C

The role of the support in CO_adsmonolayer electrooxidation on Ptnanoparticles: Pt/WO_xvs.Pt/C

Modeling and Investigation of Carbon Loss on the Cathode Electrode during PEMFC Operation

PEFC Electrocatalysts Supported on Nb-SnO₂for MEAs with High Activity and Durability: Part I. Application of Different Carbon Fillers

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Current Progress of Electrocatalyst R&D in TKK

Cited by 18 publications

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The role of the support in COadsmonolayer electrooxidation on Ptnanoparticles: Pt/WOxvs.Pt/C

The role of the support in COadsmonolayer electrooxidation on Ptnanoparticles: Pt/WOxvs.Pt/C

Modeling and Investigation of Carbon Loss on the Cathode Electrode during PEMFC Operation

PEFC Electrocatalysts Supported on Nb-SnO2for MEAs with High Activity and Durability: Part I. Application of Different Carbon Fillers

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Product

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The role of the support in CO_adsmonolayer electrooxidation on Ptnanoparticles: Pt/WO_xvs.Pt/C

The role of the support in CO_adsmonolayer electrooxidation on Ptnanoparticles: Pt/WO_xvs.Pt/C

PEFC Electrocatalysts Supported on Nb-SnO₂for MEAs with High Activity and Durability: Part I. Application of Different Carbon Fillers