Cy 241-assignment-3


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This presentation describes about recent progress in bringing down the cost of Hydrogen fuel cells. Around 3 papers were summarised and all of them belong to a timespan of 2012-2013.

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Cy 241-assignment-3

  1. 1. Recent Research Vihari Piratla(B10025)
  2. 2. Ru–Pt core–shell nano-particle ● ● ● ● This section constitutes the summary of [1]. Scientists at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory -- in research published online September 18, 2013 in the journal Nature Communications -have created a high -performing nanocatalyst that solves to a good extent the problems of high cost/rarity of Pt and poisoning of Pt catalyst upon exposure to CO. The novel core--shell structure -- ruthenium coated with platinum -- resists damage from carbon monoxide and also reduces the Pt consumption by 98%. It was observed that loss of ruthenium on start/shutdown is because of defect mediated interlayer diffusion and can be avoided by eliminating lattice defects from ruthenium particles before adding Pt.
  3. 3. Figure 1 shows the effectiveness of various bimetallic structure with respect to temperature and also observe the comparison with Pt, which does not trigger into action until 170 degrees. In conclusion this method claims a new nanoperfect Ru@Pt structure that is CO poisoning tolerant and uses 98% less platinum, they also claim that the manufacturing process is effortless and scalable and function just as well as platinum at room temperature.
  4. 4. Facile, scalable synthesis of edge halogenated graphene nanoplatelets as efficient metal-free nanocatalyst. ● ● ● ● This section summarises [2]. This paper published in June 2013, proposes edge halogenated graphene nano-platelets as a replacement for Pt crystals and also claims that this replacement has good tolerance towards methanol crossover/CO poisoning effects and long term cycle stability. It is also implied that the catalyst in itself is much cheaper because of easy synthesis and also pervasive nature of primary elements. In conclusion, a metal--free, easy to synthesise and easily available catalyst was developed and tested to be better than Pt/C and more robust than Pt/C. Though the authors state that they have to further optimise the nano-catalyst, the scope of commercialisation is very high.
  5. 5. continued (Manufacturing difficulties) ● ● ● ● Quantum mechanics calculations revealed that the electron accepting/donating ability of the heteroatom dopants created net positive/negative charges on adjacent carbon atoms in graphitic lattice to facilitate the oxygen reduction process. Thus, both the vertically- aligned nitrogen- doped carbon nanotubes (VANCNTs) and nitrogen- doped graphene (N-graphene) catalyzed an efficient four- electron ORR process with a higher electrocatalytic activity and better operation stability than the commercially available Pt/C-based electrocatalyst (Pt: 20 wt%, Vulcan XC-72R). But the manufacturing process stood as an impediment, classical CVD methods are not scalable. Proposed a catalyst which can be easily synthesised and scalable.
  6. 6. continued(details of manufacturing) Ball milling of graphite with halogen produces edge halogenated nanoplatelets of Graphene(XGnPs).
  7. 7. continued (Durability tests and efficacy tests) ● ● ● In a test of durability, electrodes coated with XGnP's maintained 85.6 to 87.4 percent of their initial current after 10,000 cycles while platinum electrodes maintained only 62.5 percent. The performance of graphene based catalysts was unaffected with induction of CO impurity with Hydrogen fuel. Also in comparison with the Pt/C commercially available catalyst: a cathode coated with iodine -edged nanoplatelets performed best. A cathode coated with bromin e-edged nanoparticles generated 7 percent less current than the commercial cathode coated with platinum, the chlorin e-edged nanoplatelets 40 percent less.
  8. 8. Nano-catalyst based on carbon-nanotubes graphene complexes ● ● ● ● ● This section summarises [3]. For the study, the Stanford team used multi-walled carbon nanotubes consisting of two or three concentric tubes nested together. The group showed that shredding the outer wall, while leaving the inner walls intact, enhances catalytic activity in nanotubes, yet does not interfere with their ability to conduct electricity. A typical carbon nanotube has few defects, but defects are actually important to promote the formation of catalytic sites and to render the nanotube very active for catalytic reactions. This paper also obviates some of the misconceptions and states that metal defects in the catalyst increases catalytic capabilities and hence should not be ignored.
  9. 9. continued(depiction) Authors claim that though the outer wall is unzipped the conductivity remains intact because of the inner wall and hence can help in charge mobility. This nano catalyst has performance commensurate with Pt/C. This figure also depicts iron and nitrogen impurities which contribute in allaying the capability.
  10. 10. Summary ● ● ● We are evidencing a revolution in the research of nano catalysts with the advent of Nano-science and nano imaging techniques like STEM. Nanocatalysts have a larger scope in catalysis because of ○ increased surface area, ○ possibility of producing defect free and hence very conductive. Also because of the enhanced imaging techniques, the pioneers are able to observe the factors that influence the active sites and catalytic abilities and thus leading to better catalysts like NickelPhosphide.
  11. 11. Summary(continued) ● ● ● ● We have seen metal--free catalysts that can function better or just as well as Pt/C and also have seen modification to Pt catalysts to nano-catalysts to improve the robustness and alleviate cost. These fuel cells can be much cheaper because of the reduced catalyst cost which constitutes 40% and also reduced cost of hydrogen fuel because of the relaxed constraint of CO poisoning. The day when HFC's replace IC engines is near and can be one stop solution for depriving sources of oils and green-house gases. Seems like, only possible piece of puzzle that needs to be solved is efficient(Volume/weight ratio) and safe storage of Hydrogen.
  12. 12. References 1. Yu-Chi Hsieh, Yu Zhang, Dong Su, Vyacheslav Volkov, Rui Si, Lijun Wu, Yimei Zhu, Wei An, Ping Liu, Ping He, Siyu Ye, Radoslav R. Adzic & Jia X Wang (2013) Ordered bilayer ruthenium–platinum core-shell nanoparticles as carbon monoxidetolerant fuel cell catalysts. Nature Communications 4, Article number: 2466 doi: 10.1038/ncomms3466 2. Jeon, I., Choi, H., Choi, M., Seo, J., Jung, S., Kim, M., Zhang, S., Zhang, L., Xia, Z., Dai, L. and Others. 2013. Facile, scalable synthesis of edge-halogenated graphene nanoplatelets as efficient metal- free eletrocatalysts for oxygen reduction reaction. Li, Y., Zhou, W., Wang, H., Xie, L., Liang, Y., Wei, F., Idrobo, J., Pennycook, S. and Dai, H. 2012. An oxygen reduction electrocatalyst based on carbon nanotube-graphene complexes. Nature nanotechnology, 7 (6), pp. 394--400. 3.