Improving the Capacitance of Graphene Aerogel Electrodes via a Facile Ion-intercalation Strategy (oral presentation, ENFL #162, 253rd ACS National Meeting, San Francisco, CA, 2017)

1. Improving the Capacitance of Graphene
Aerogel Electrodes via a Facile Ion-
intercalation Strategy
Tianyu LIU
Yat Li Lab
Department of Chemistry and Biochemistry
University of California, Santa Cruz
04/2017

2. UC Santa Cruz

3. Li Lab
Chem. Soc. Rev., 2012, 41, 5654-5671
ACS Nano, 2013, 7, 8728–8735
Adv. Mater. 2014, 26, (17), 2676
Photo-electrochemical
Water Splitting
Supercapacitor
Microbial Fuel Cell
Sustainable
Energy

4. Outline
 What Are Supercapacitors?
 3D-printed Graphene Aerogel Electrodes
 Three-step Intercalation Strategy
 Experimental Results
 Summary

5. Background
(Supercapacitors)

6. Structure of Supercapacitors
Charge storage devices
Large surface area
5 μm
ZnO Nanowires
10 μm
Graphene Aerogel

7. Capacitance
Charge storage ability
Charge storage mechanisms
Electrical Double
Layer Capacitance
Pseudo-
capacitance
Activated Carbon,
CNT, Graphene etc.
Conjugated polymers,
metal oxides etc.
𝑪𝒂𝒑𝒂𝒄𝒊𝒕𝒂𝒏𝒄𝒆 =
𝐶𝑎𝑝𝑎𝑐𝑖𝑡𝑦
𝑃𝑜𝑡𝑒𝑛𝑡𝑖𝑎𝑙 𝑊𝑖𝑛𝑑𝑜𝑤

8. 3D Printed Periodical
Macro-porous Graphene
Aerogels
Nano Lett., 16, 3448-3456 (2016)

9. 3D Printing
1 mm

10. Electrochemical Performance
 Compare with a bulk graphene aerogel electrode

11. Three-step Ion
Intercalation Strategy
ChemNanoMater, 2, 635-641 (2016)

12. Ion Intercalation Strategy
 Mechanism
  
Graphitic Structures

13. Ion Intercalation Strategy
 Mechanism
 First step: surface roughening
(-5 V, 2 h in propylene carbonate, two-electrode)
  
CG + Li+ +e- → CG
--Li+
[Electrolyte co-intercalation is possible]

Graphitic Structures

14. Ion Intercalation Strategy
 Mechanism
  
 Second & third step: surface functionalization with oxygen-functionalities
(+5 V, 2 h in propylene carbonate, two-electrode system)
CG + ClO4
- → CG
+-ClO4
-+e-

 CG
+-ClO4
- + H2O → CG-OH + HClO4
4CG
+-ClO4
- + 2H2O → 4CG + O2 +4H++4ClO4
-
Graphitic Structures

15. Trial One
(Graphitic Paper)
ChemNanoMater, 2, 635-641 (2016)

16. Morphology Evolution
 More wrinkles were formed after the two-step treatment;
 The enhanced surface area is beneficial for achieving higher charge storage capacity as more active sites
are created.
Surface Area: 14.0 m2/g 73.9 m2/g
0 r
C
d
S 


17. Surface Oxidation
 Infra-red spectra (left): hydroxyl groups (-OH) and carbonyl groups (C=O) were
introduced after the treatment.
 X-ray photoelectron spectroscopy (right): –OH and C=O functional groups were
introduced after the treatment.
Pseudo-capacitance

18. Electrochemical Performance
 The treated sample exhibited much higher capacitance than the
untreated sample;
 The treated sample showed near-ideal capacitive behavior.
Capacitance retention: 84.04%
(When current increase from 0.5 mA/cm2 to 5 mA/cm2)

19. Trial Two
(3D-printed Graphene Aerogels)
ChemNanoMater, 2, 635-641 (2016)
1 mm

20. Morphological Evolution

21. Electrochemical Performance
 CyclicVoltammogram  Rate Capability

22. Electrochemical Performance
 Cycling Stability
97% capacitance retention

23. Summary

24. Features
Three-step
Ion
Intercalation
StrategyMaintain
structural
integrity
No need
for post-
reduction
Effective in
Enhancing
Capacitance
of Graphene
Structures
ChemNanoMater, 2, 635-641 (2016)

25. Acknowledgements
Our Collaborators
Prof. Yat Li Group, UCSC
Cheng Zhu Marcus
Worsley
Christopher
Spadaccini
Eric
Duoss
Chancellor’s Dissertation-year Fellowship