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Mesoporous Iron Oxide Pseudocapacitive Electrodes with Mutually High Mass Loadings and Excellent Rate Capability

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ENFL #188, ACS Spring 2019 National Meeting

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Mesoporous Iron Oxide Pseudocapacitive Electrodes with Mutually High Mass Loadings and Excellent Rate Capability

  1. 1. Mesoporous Iron Oxide Pseudocapacitive Electrodes with Mutually High Mass Loadings and Excellent Rate Capability Tianyu LIU Yat Li Lab Department of Chemistry and Biochemistry University of California, Santa Cruz 04/2019 ENFL #188
  2. 2. Outline  Background of Supercapacitors  Motivation – Make Hematite Great?  Synthesis and Characterizations  Electrochemical Performances  Summary
  3. 3. Outline  Background of Supercapacitors  Motivation – Make Hematite Great?  Synthesis and Characterizations  Electrochemical Performances  Summary
  4. 4. Supercapacitors ❑ Electrochemical energy storage devices ChargingTime LiuT. et al., J. Mater. Chem.A, 2017, 5, 17705-17733 < 1s to ~100 s ~ hours (Supercapacitors) (Batteries) vs.
  5. 5. Capacitance 𝐂𝐚𝐩𝐚𝐜𝐢𝐭𝐚𝐧𝐜𝐞(𝐅) = Capacity (C) Potential Window (V) A measure of the amount of charge (energy) stored ❑ A figure-of-merit of supercapacitors and their electrodes
  6. 6. ❑ Mechanisms Electrical Double Layer Capacitance Pseudo- capacitance Activated Carbon, CNT, Graphene etc. Conjugated polymers, metal oxides etc. ENFL #547 4/3, 2:25 pm – 2:40 pm West Hall B4,Theater 13, OCCC Capacitance
  7. 7. Outline  Background of Supercapacitors  Motivation – Make Hematite Great?  Synthesis and Characterizations  Electrochemical Performances  Summary
  8. 8. The Pros and Cons of Hematite • Pseudocapacitive • Inexpensive • Environmentally benign • Stable • Poorly conductive (e-) PROS CONS Iron oxide, hematite (α-Fe2O3)
  9. 9. Charge Carrier Kinetics Low mass loading e transport Ion diffusion High mass loading >5-10 mg cm-2 Commercially promising Capacitance Charge/Discharge Rate o Good rate capability o Low capacitance 0 Capacitance Charge/Discharge Rate o High capacitance o Poor rate capability 0
  10. 10. Outline  Background of Supercapacitors  Motivation – Make Hematite Great?  Synthesis and Characterizations  Electrochemical Performances  Summary
  11. 11. Ion Percolation ❑ Introducing pores Small Pores Intermediate Pores Large Pores Ion flux • High capacitance • Poor rate capability • Good rate capability • Limited capacitance Mesopore (2-200 nm) solvent
  12. 12. Our Design Mesoporous Iron Oxide Films
  13. 13. Our Design ❑ Introducing glucose Adv. Energy Mater., 2018, 8, 1801784
  14. 14. Our Design ❑ Formation of mesopores Adv. Energy Mater., 2018, 8, 1801784
  15. 15. Pore Size Controllability [Glucose] Low-magTEM Images High-magTEM Images 0.04 M 0.07 M 0.10 M 5 nm 20 nm Adv. Energy Mater., 2018, 8, 1801784 Hem-G0.04 Hem-G0.07 Hem-G0.10
  16. 16. Pore Size Controllability ❑ N2-physisorption results Adv. Energy Mater., 2018, 8, 1801784
  17. 17. Outline  Background of Supercapacitors  Motivation – Make Hematite Great?  Synthesis and Characterizations  Electrochemical Performances  Summary
  18. 18. Ion Diffusion Kinetics ❑ Electrochemical impedance spectroscopy Adv. Energy Mater., 2018, 8, 1801784 Slope ∝ (ion-diffusion resistivity)-1
  19. 19. Rate Capability Performances Adv. Energy Mater., 2018, 8, 1801784
  20. 20. Cycling Stability Adv. Energy Mater., 2018, 8, 1801784 Increased charge- transfer resistance
  21. 21. Cycling Stability Surface hydration ❑ X-ray photoelectron spectroscopy Adv. Energy Mater., 2018, 8, 1801784
  22. 22. Outline  Background of Supercapacitors  Motivation – Make Hematite Great?  Synthesis and Characterizations  Electrochemical Performances  Summary
  23. 23. Conclusion o Introducing glucose in the hydrothermal system o Mesoporous iron oxide films with high mass loadings o Facilitated ion diffusion and improved rate capability 5 nm
  24. 24. Acknowledgements Prof. Yat Li Group, UCSC (2017) Dr. Yu Song
  25. 25. ENFL #547 2:25 pm – 2:40 pm,Apr. 3rd West Hall B4,Theater 13, OCCC Blending NH3 with N2 for Synthesis of N-Doped Carbon Aerogels

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