Deactivation of Pt/VC proton exchange membrane fuel cell cathodes by SO2, H2S and COS

Gould, Benjamin D.; Батурина, О. А.; Swider‐Lyons, Karen

doi:10.1016/j.jpowsour.2008.11.072

Cited by 104 publications

(102 citation statements)

References 48 publications

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“…f. Some of the explanations for the irreversible loss due to H 2 S poisoning are deposition of organosulfur [ 28 ], sulfur induced Pt agglomeration, sub-surface sulfur and its interaction with Pt, formation of platinum sulfides and oxides that are difficult to reduce and the migration of Pt clusters due to loss in the metal-support interaction. This deactivation of Pt sites is reported to be same regardless of the type of sulfur contamination (H 2 S, SO 2 or COS) [29].…”

Section: Introductionmentioning

confidence: 80%

“…It is yet not clear as to how much recovery via electrochemical oxidation is possible on the cathode after sulfur poisoning. Regardless, polarization curves have so far been the only means to compare the recovery of sulfur poisoned cathodes as well [29,43,47]. Figure 9 shows the first ten cycles of a cyclic voltammogram obtained on the PEM fuel cell anode after adsorption with H 2 S at 25 °C and 1 atm.…”

Section: Figure 5: Current Potential Curves Obtained At 70 °C and 1 Amentioning

confidence: 99%

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Analysis of sulfur poisoning on a PEM fuel cell electrode

Sethuraman

Weidner

2010

Electrochimica Acta

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The extent of irreversible deactivation of Pt towards hydrogen oxidation reaction (HOR) due to sulfur adsorption and subsequent electrochemical oxidation is quantified in a functional PEM fuel cell. At 70 °C, sequential hydrogen sulfide (H 2 S) exposure and electrochemical oxidation experiments indicate that as much as 6% of total Pt sites are deactivated per monolayer sulfur adsorption at open circuit potential of a PEM fuel cell followed by its removal. The extent of such deactivation is much higher when the electrode is exposed to H 2 S when the fuel cell is operating at a finite load, and is dependent on the local overpotential and the duration of exposure. Regardless of this deactivation, the H 2 /O 2 polarization curves obtained on postrecovery electrodes do not show performance losses suggesting that such performance curves alone cannot be used to assess the extent of recovery due to sulfur poisoning. A concise mechanism for the adsorption and electro-oxidation of H 2 S on Pt anode is presented. H 2 S dissociatively adsorbs onto Pt as two different sulfur species and at intermediate oxidation potentials, undergoes electro-oxidation to sulfur and then to sulfur dioxide (SO 2 ). This mechanism is validated by charge balances between hydrogen desorption and sulfur electrooxidation on Pt. The ignition potential for sulfur oxidation decreases with increase in temperature, which coupled with faster electro-oxidation kinetics result in the easier removal of adsorbed sulfur at higher temperatures. Furthermore, the adsorption potential is found to influence sulfur coverage of an electrode exposed to H 2 S. As an implication, the local potential of a PEM fuel cell anode exposed to H 2 S contaminated fuel should be kept below the equilibrium potential for sulfur oxidation to prevent irreversible loss of Pt sites.

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Section: Introductionmentioning

confidence: 80%

Section: Figure 5: Current Potential Curves Obtained At 70 °C and 1 Amentioning

confidence: 99%

Analysis of sulfur poisoning on a PEM fuel cell electrode

Sethuraman

Weidner

2010

Electrochimica Acta

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“…The quantitative method they used was a bit different from ours used here, since they did not consider the recovery of the area of adsorption/desorption of hydrogen in each cycling of cycle voltammetry (CV). Gould et al [12] studied the effects of SO 2 , COS and H 2 S on the performance of Pt/VC, and found they had the similar poisoning behaviors, which indicated a similar poisoning mechanism. Baturina et al [14] studied the SO 2 poisoning behavior on Pt 3 Co/VC and Pt/VC fuel cell catalysts, and found that Pt 3 Co/VC was easier to recover the performance, despite that it was more susceptive to SO 2 poisoning than Pt/VC at a given platinum loading.…”

Section: Introductionmentioning

confidence: 99%

“…There are literatures reporting the poisoning behaviors of different kinds of sulfur-contained species on PEMFC [12], but the effects of sulfur with different valences on the performance of Pt only draw minimal attentions. Since the catalytic layers are affected by SO 2 most severely, literatures have also paid lots of attentions to catalysts [10,[13][14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

A quantitative research on S- and SO2-poisoning Pt/Vulcan carbon fuel cell catalyst

Xie

Shao

Zhang

et al. 2012

Electrochimica Acta

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a b s t r a c tA quantitative research on S and SO 2 poisoning Pt/Vulcan carbon (Pt/VC) catalysts for fuel cells was conducted by the three-electrode method. Pt/VC electrodes were contaminated by submersion in a SO 2 -containing solution made up of 0.2 mM Na 2 SO 3 and 0.5 M H 2 SO 4 for different periods of time, and held at 0.05 V (vs. RHE) in 0.5 M H 2 SO 4 solutions in order to gain zero-valence sulfur (S 0 ) poisoned electrodes. The sulfur coverage of Pt was determined from the total charge consumed as the sulfur was oxidized from S 0 at 0.05 V (vs. RHE) to sulfate at >1.1 V (vs. RHE). The summation of initial coverage of S 0 (Â S ) and coverage of H (Â H ) are approximately equal to 1 (Â H + Â S = 1) when 0.5 < Â H < 1, which gives an easy way to figure out the quantity of sulfur adsorbed on Pt/VC. As to SO 2 poisoned Pt/VC, the catalytic activity of oxygen reduction reaction (ORR) decreases linearly with the amount of SO 2 adsorbed on the Pt nanoparticles when 0.45 < Â H < 0.81. When the adsorbed SO 2 was reduced to S 0 , the mass activity was greatly recovered, and the area specific activity was even higher than the unpoisoned Pt/VC.

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“…They suggested that SO 2 molecules could be adsorbed on the Pt catalyst without charge transfer at 0.65 V, oxidized above 0.65 V and reduced below it. To date, some methods, such as cycle voltammogram (CV) scans, open circuit voltage (OCV) and I-V measurements, have already been used to handle with SO 2 poisoning [2,7,8]. Additionally, Ma et al [9] confirmed that activated carbon could be used as air filtration adsorbent to prevent SO 2 from poisoning the cell catalyst.…”

Section: Introductionmentioning

confidence: 99%