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Electrochemical Characterization of Qraphene-based Cathode Electrode for Lithium-air Battery

Ahadi, Sina | 2022

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 54801 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Dolati, Abolghasem
  7. Abstract:
  8. The air cathode of li-air batteries has been identified as a key factor affecting the overall performance of Li-air batteries. Graphene-based cathodes have been investigated as cathode catalysts for lithium-air batteries due to their high activity in accelerating and facilitating oxygen reduction reaction (ORR). In this study at first, graphene oxide was synthesized using Hummers’ method, and then it has been reduced via hydrothermal methode. To increase electrocatalytic properties of the sample Cobalt oxide nanoparticles has been precipitated on reduced graphene oxide, and it has also been doped with Nitrogen. Three samples of reduced graphene aerogel (GA), Nitrogen doped graphene aerogel (NGA) and Nitrogen doped graphene aerogel with Cobalt oxide nanoparticles (NGACo) have been prepared. In this research urea was used as Nitrogen source. From XRD analysis, proper reduction of graphene oxide, and evolution of cobalt oxide from cobalt carbonat have been confirmed. From FT-IR analysis proper elimination of Oxygen containing functional groups, and bonding of Nitrogen to Carbon and reduction of sp2 hybridization in Nitrogen doped samples have been observed. Reduction of sp2 hybridization is also apparent from increase of ID/IG. 2D peak observed in Raman spectrum of NGA and NGACo samples is a sign of lower rGO sheet stacking and as a result increase in specific surface area. Specific aera of the samples are determined by BET and they are 56 m2/g, 110 m2/g and 430 m2/g for GA, NGA and NGACo respectively, which confirms what has been said. Linear polarization results show that the NGACo has the most positive ORR onset potential (+0.556 V vs SHE) among the other samples (+0.407 and +0.315V vs SHE for GA, and NGA, respetively). Also NGACo sample has considerably larger cathodic current density (-6.91 mA⁄cm^2 ) than the other samples (-2.6 and -3.69 mA⁄cm^2 for GA and NGA, respetively) which demonstrates the positive effect of doped Nitrogen and also Cobalt oxide percipitates on the current of a electrode. Cathodic slope of GA, NGA, NGACo measured to be 44.6, 39.2, and 39 mV/decade which is far less than what is recorded in other articles which implied a more facile electron transfer in samples synthesized in this research
  9. Keywords:
  10. Lithium-air Batteries ; Nitrogen Doped Graphene ; Oxygen Reduction Reaction ; Graphene-Based Cathode ; Aerogel Synthesis ; Nitrogen Doped Graphene Arogel

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