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Highly efficient oxygen reduction electrocatalysts based on winged carbon nanotubes.

Cheng Y, Zhang H, Varanasi CV, Liu J - Sci Rep (2013)

Bottom Line: We found that the outer-walls of a special type of carbon nanotubes/nanofibers, when selectively oxidized, unzipped and exfoliated, form graphene wings strongly attached to the inner tubes.After doping with nitrogen, the winged nanotubes exhibited outstanding activity toward catalyzing the ORR through the four-electron pathway with excellent stability and methanol/carbon monoxide tolerance.While the doped graphene wings with high active site density bring remarkable catalytic activity, the inner tubes remain intact and conductive to facilitate electron transport during electrocatalysis.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Chemistry, Duke University, Durham, NC 27708 United States [2] Center for the Environmental Implication of NanoTechnology (CEINT), Duke University, Durham, NC 27708 United States.

ABSTRACT
Developing electrocatalysts with both high selectivity and efficiency for the oxygen reduction reaction (ORR) is critical for several applications including fuel cells and metal-air batteries. In this work we developed high performance electrocatalysts based on unique winged carbon nanotubes. We found that the outer-walls of a special type of carbon nanotubes/nanofibers, when selectively oxidized, unzipped and exfoliated, form graphene wings strongly attached to the inner tubes. After doping with nitrogen, the winged nanotubes exhibited outstanding activity toward catalyzing the ORR through the four-electron pathway with excellent stability and methanol/carbon monoxide tolerance. While the doped graphene wings with high active site density bring remarkable catalytic activity, the inner tubes remain intact and conductive to facilitate electron transport during electrocatalysis.

No MeSH data available.


Related in: MedlinePlus

Comparison of the selectivity and durability of the N-wNT catalyst with Pt/C: (a) with the presence of 1 M methanol (b) 10% (v/v) carbon monoxide and (c) relative current as a function of time at 0.5 V (1600 rpm).
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f4: Comparison of the selectivity and durability of the N-wNT catalyst with Pt/C: (a) with the presence of 1 M methanol (b) 10% (v/v) carbon monoxide and (c) relative current as a function of time at 0.5 V (1600 rpm).

Mentions: The N-wNT catalyst was further tested for possible fuel crossover and poisoning effects in the presence of methanol and carbon monoxide (CO), respectively. For comparison, the behavior of Pt/C under the same conditions was also studied. The strong amperometric response of N-wNT was very stable upon introduction of 1 M methanol (Figure 4a). In contrast, more than 40% of the initial electrocatalytic current was lost for Pt/C. The high selectivity could be attributed to the lower ORR potential than that required for oxidization of methanol using the N-wNT catalyst6. The effect of CO on the electrocatalytic activity of N-wNT was also tested since CO poisoning is a major concern for noble-metal catalysts. Being nonmetallic, the activity of N-wNT was stable even with 10% (v/v) CO (Figure 4b), whereas the Pt/C catalyst was rapidly poisoned with dramatically decreased current density (~40% within 300 s). Hence, it is clear that the N-wNT catalyst have excellent tolerance for both methanol and CO, indicating high selectivity toward catalyzing the ORR. The reliability of the catalyst was also examined and compared with that of Pt/C by recording the current at 0.5 V and 1600 rpm using RDE and the current retentions were compared in Figure 4c. Additional data on long-term stability measurement is provided in Figure S6. The results show that the N-wNT catalyst exhibite good stability (~30% activity loss after 12 hours operation at 0.5 V) and is more stable than commercial Pt/C catalyst.


Highly efficient oxygen reduction electrocatalysts based on winged carbon nanotubes.

Cheng Y, Zhang H, Varanasi CV, Liu J - Sci Rep (2013)

Comparison of the selectivity and durability of the N-wNT catalyst with Pt/C: (a) with the presence of 1 M methanol (b) 10% (v/v) carbon monoxide and (c) relative current as a function of time at 0.5 V (1600 rpm).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3824170&req=5

f4: Comparison of the selectivity and durability of the N-wNT catalyst with Pt/C: (a) with the presence of 1 M methanol (b) 10% (v/v) carbon monoxide and (c) relative current as a function of time at 0.5 V (1600 rpm).
Mentions: The N-wNT catalyst was further tested for possible fuel crossover and poisoning effects in the presence of methanol and carbon monoxide (CO), respectively. For comparison, the behavior of Pt/C under the same conditions was also studied. The strong amperometric response of N-wNT was very stable upon introduction of 1 M methanol (Figure 4a). In contrast, more than 40% of the initial electrocatalytic current was lost for Pt/C. The high selectivity could be attributed to the lower ORR potential than that required for oxidization of methanol using the N-wNT catalyst6. The effect of CO on the electrocatalytic activity of N-wNT was also tested since CO poisoning is a major concern for noble-metal catalysts. Being nonmetallic, the activity of N-wNT was stable even with 10% (v/v) CO (Figure 4b), whereas the Pt/C catalyst was rapidly poisoned with dramatically decreased current density (~40% within 300 s). Hence, it is clear that the N-wNT catalyst have excellent tolerance for both methanol and CO, indicating high selectivity toward catalyzing the ORR. The reliability of the catalyst was also examined and compared with that of Pt/C by recording the current at 0.5 V and 1600 rpm using RDE and the current retentions were compared in Figure 4c. Additional data on long-term stability measurement is provided in Figure S6. The results show that the N-wNT catalyst exhibite good stability (~30% activity loss after 12 hours operation at 0.5 V) and is more stable than commercial Pt/C catalyst.

Bottom Line: We found that the outer-walls of a special type of carbon nanotubes/nanofibers, when selectively oxidized, unzipped and exfoliated, form graphene wings strongly attached to the inner tubes.After doping with nitrogen, the winged nanotubes exhibited outstanding activity toward catalyzing the ORR through the four-electron pathway with excellent stability and methanol/carbon monoxide tolerance.While the doped graphene wings with high active site density bring remarkable catalytic activity, the inner tubes remain intact and conductive to facilitate electron transport during electrocatalysis.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Chemistry, Duke University, Durham, NC 27708 United States [2] Center for the Environmental Implication of NanoTechnology (CEINT), Duke University, Durham, NC 27708 United States.

ABSTRACT
Developing electrocatalysts with both high selectivity and efficiency for the oxygen reduction reaction (ORR) is critical for several applications including fuel cells and metal-air batteries. In this work we developed high performance electrocatalysts based on unique winged carbon nanotubes. We found that the outer-walls of a special type of carbon nanotubes/nanofibers, when selectively oxidized, unzipped and exfoliated, form graphene wings strongly attached to the inner tubes. After doping with nitrogen, the winged nanotubes exhibited outstanding activity toward catalyzing the ORR through the four-electron pathway with excellent stability and methanol/carbon monoxide tolerance. While the doped graphene wings with high active site density bring remarkable catalytic activity, the inner tubes remain intact and conductive to facilitate electron transport during electrocatalysis.

No MeSH data available.


Related in: MedlinePlus