Welcome to Chem 179 Nanomaterials for Supercapacitors Week #2 Electrical Double Layer Capacitance Tim/Tianyu
E-mail:
[email protected] Office Hour: By Appointment Lab: PSB 198
Outline Mechanism of Electrical Double Layer Formation
Models
Electrical Double Layer Capacitance Characteristics Common Electrodes
Lab Section Hydrothermal Reaction
Mechanism
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EDL Electrode
Formation of Electrical Double Layer
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Bulk Electrolyte
Models of Electrical Double Layer Helmholtz Model Rigid layer of ions at the interface Rigid Layer
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Crude Model
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Φ
Hermann von Helmholtz
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Models of Electrical Double Layer Gouy-Chapman Model Diffusive layer of ions at the interface Diffusive Layer
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2 r 0 n0 ze0 C ze cosh kT 2kT Φ
Louis Georges Gouy
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Models of Electrical Double Layer Gouy-Chapman-Stern Model Rigid + Diffusive layer of ions at the interface IHP OHP
Diffusive Layer
IHP: Inner Helmholtz Plane ~ 1 nm OHP: Outer Helmholtz Plane ~ 1-20 nm
Φ
Otto Stern
2 r 0 n0 ze0 ze cosh kT 2kT C x2 2 r 0 n0 ze0 1+ cosh ze kT 2kT r 0
Models of Electrical Double Layer Gouy-Chapman-Stern Model A more realistic picture – solvation of ions
www2.chemistry.msu.edu
Electrical Double Layer Capacitance
Characteristics of EDLC Fast charge and discharge rate. Rectangular cyclic voltammetry (CV) diagram A theoretical CV diagram of a 3 F EDL capacitor (100 mV/s)
http://www.gamry.com/application-notes
An experimental CV diagram of a Ndoped graphene aerogel (100 mV/s)
Characteristics of EDLC Fast charge and discharge rate. Symmetric and triangular chrono-potential (CP) profile Potential (V)
A theoretical CP diagram of an EDL capacitor (100 mV/s)
Time (s)
An experimental CV diagram of a N-doped graphene aerogel (100 mV/s)
Characteristics of EDLC Fast charge and discharge rate. High power density
Low specific capacitance (F/g) Activated Carbon Biomass derived carbon Carbon nanotubes Graphene films Graphene aerogels
Low energy density
~100-200 F/g 550 F/g (single layer, theoretical) ~100-200 F/g (experimental) Due to stacking of graphene layers
Characteristics of EDLC Excellent Stability Usually >90% capacitive retention after 10000 charge-discharge cycles. 100% retention
Activated Carbon
Commonly used in commercial supercapacitors
Large surface area (~1200 m2/g)
ACS Sustainable Chemistry & Engineering 2014, 2, (7), 1592-1598
Biomass Derived Carbon
ACS Nano 2013, 7, (4), 3589-3597
Carbon Nanotubes
Journal of Physical Chemistry C 2015, 119, (7), 3538-3544
Carbon Nanotubes Influence of wall # on surface area:
SWNT
2WNT Carbon 2001, 39, (4), 507-514
3WNT 4WNT
5WNT 10WNT
20WNT
Graphene Film
Theoretical Surface Area 2630 m2/g (single layer)
Advanced Materials 2013, 25, (35), 4879-4885
Graphene Film Synthesis – Hummer’s Method + Reduction
Exfoliation + Reduction
Oxidation
Graphitic Oxide Reduced graphene oxide
Nanoscale, 2012, 4, 3977–3982
Carbon Nanotubes Exfoliation of CNT to produce graphene H2SO4, HNO3, KMnO4
Journal of Power Sources 2011, 196, (11), 5209-5214
Carbon Nanotubes Exfoliation of CNT to produce graphene
ACS Applied Materials & Interfaces 2015, 7, (5), 3110-3116
Graphene Aerogel
ACS Nano 2010, 4, (7), 4324-4330
Graphene Aerogel Concentration of GO is a key factor to form graphene aerogel
ACS Nano 2010, 4, (7), 4324-4330
Composite Materials Composite/hybrid material: A material consisted of two or more materials Graphene + CNT
Chemistry of Materials 2011, 23, (21), 4810-4816
Composite Materials Composite/hybrid material: A material consisted of two or more materials Graphene + CNT
ACS Nano 2015, 9, (2), 2018-2027
Take-home Message Two important factors for good EDL electrodes:
Excellent electrical conductivity Large surface area
Hydrothermal Synthesis
Introduction What is hydrothermal synthesis/reaction? Use water as solvent Reaction @ extremely high pressure Reaction @ high temperature
Supercritical state
Introduction Steel autoclave Teflon-lined reactor
Synthesis Ni foam as substrate
www.aliexpress.com
www.firstnano.com
Synthesis – Biomass Derived Carbon Synthesis of carbon coated Ni foam electrode
N2
0.1 M Glucose
800 oC, 1 h
150 oC, 5 h
Ni Foam
Carbonaceous Film
Carbon Film
Ni Foam
Ni Foam
Synthesis - Graphene Synthesis of graphene coated Ni foam electrode
0.5 g/L GO Solution 150 oC, 5 h
Graphene Film Ni Foam
Ni Foam
Extracurricular Readings Papers are available on eCommons.
[1] Zhi, M.; et al., Effects of Pore Structure on Performance of An ActivatedCarbon Supercapacitor Electrode Recycled from Scrap Waste Tires. ACS Sustainable Chemistry & Engineering 2014, 2, (7), 1592-1598 [2] Wu, X.; et al., Biomass-Derived Sponge-like Carbonaceous Hydrogels and Aerogels for Supercapacitors. ACS Nano 2013, 7, (4), 3589-3597. [3] Chen, T.; Dai, L., Carbon nanomaterials for high-performance supercapacitors. Materials Today 2013, 16, (7–8), 272-280. [4] Worsley, M. A. et al., Synthesis of Graphene Aerogel with High Electrical Conductivity. Journal of the American Chemical Society 2010, 132, (40), 1406714069
Extracurricular Readings Papers are available on eCommons.
[5] Pham, D. T. et al., Carbon Nanotube-Bridged Graphene 3D Building Blocks for Ultrafast Compact Supercapacitors. ACS Nano 2015, 9, (2), 2018-2027 [6] Sahu, V.; et al., Ultrahigh Performance Supercapacitor from Lacey Reduced Graphene Oxide Nanoribbons. ACS Applied Materials & Interfaces 2015, 7, (5), 3110-3116
End of Lecture #2 Thank You! See you in the lab
