Origin of Enhancements Using RGO

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A look at the enhancements in battery operation by utilizing reduced graphene oxide as an electrode substrate.
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Origin of Enhancements Using RGO

  1. 1. ACS Catal., 2012, 2, pp 807–816 DOI: 10.1021/cs3001286 1
  2. 2. MotivationReduced graphene oxide is composited with many intercalation compounds inmany recent studies, with significant improvement in performance. But…Why? 2
  3. 3. Approach•Prepare Reduced Graphene Oxide (RGO)/ -MnO2 Nanowire Composite•Synthesize different lengths of nanowires to differentiate effects inherent to MnO2from those afforded by RGO•Characterize composites using electron microscopy and x-ray diffraction•Evaluate the electrochemical response of the composite electrode usingchronocoulometry and impedance spectroscopy•Determine the overall cycling characteristics of the optimized electrode 3
  4. 4. Morphology•Short nanowires (SNW) exhibit higher crystallinity•RGO enhances crystallinity during synthesis•Mixed morphology (alpha/ramsdellite MnO2)•Mn2O3 and Mn3O4 impurities Synthesis adapted from: Chen, S., et. al, ACS Nano, 2010, 4(5), 2822-2830 4
  5. 5. RGO in 3-D•Wrinkling characteristic of RGO generates 3-D macrostructure•Intimate contact between nanowires and RGO 5
  6. 6. RGO Self-Repair of Impurities 6
  7. 7. Charge-Discharge Cyclinga – rLNWb – LNW Controls:c – rSNW LNW + 30% Cd – SNW r + LNWe – LNW + 30% Cf – r + LNW 7
  8. 8. EIS and ChronocoulometryElectron Storage on RGO: Lightcap, I. V., Kosel, T. H., Kamat, P. V., Nano Lett., 2010, 4, 577–583 8
  9. 9. Summary•Utilized -MnO2 nanowires of different lengths to probe the role ofRGO in electrochemical energy storage electrodes•RGO serves to increase crystallinity in the final active material andcatalyzes self-repair of partially-oxidized manganese oxide impurities•RGO significantly reduces the charge-transfer impedance at theelectrode-electrolyte interface•RGO acts as kinetic mediator between electrons and lithium ions via itssurface storage of electrons and enhanced diffusion of Li+ through its 3-Dmacrostructure 9
  10. 10. Thank You! This work can be found in ACS Catalysis ACS Catalysis 2, 807-816 2012 DOI: 10.1021/cs3001286More information on the Kamat Research Group can be found at: www.kamatlab.com 10

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