Nano-Applications for Energy
Xiangwu Zhang
Fiber and Polymer Science
Department of Textile Engineering, Chemistry and Science
North Carolina State University
Raleigh, NC 27695-8301
Tel: 919-515-6547
Email: xiangwu_zhang@ncsu.edu
Fuel cells
Batteries
Solar cells
• Nanostructured and multifunctional polymer, composite,
fiber, and textile materials with an emphasis on energyrelated applications (such as fuel cells, batteries, and
solar cells)
What is a Fuel Cell?
Fuel Cell
• A fuel cell is an energy conversion system that converts the
chemical energy of hydrogen (or other fuels) directly into electrical
energy
Benefits and Applications
Benefits
• Energy Security
• Environment Friendly
• High Efficiency
• Jobs and the Economy
Applications
Mobile
Ford Hybrid Hydrogen Focus Vehicle
Stationary
UTC Fuel Cells
Portable
Toshiba
Smart
Fuel Cells
Manhattan
Scientifics
Ballard Power
Systems
How Fuel Cell Works?
Electron
Anode
Fuel
Electrolyte Cathode
Oxygen
H+
H+
2H2 Æ 4H+ + 4eH+
O2 + 4H+ + 4e- Æ 2H2O
Water/Heat
Overall reaction: 2H2 + O2 Æ 2H2O + electrical energy
• A fuel cell is an energy conversion system that converts the
chemical energy of hydrogen (or other fuels) directly into electrical
energy
Nanostructured Materials for Fuel Cells
a) Nanofiber Electrodes
c) Hybrid Electrolyte Membranes
b) Carbon Nanotube Electrodes
d) Neutron Fuel Cell Imaging
a) Nanofiber Electrodes
Fuel Cell Electrodes
Proton
Conductor
Pt Supported on
Carbon Particle
Carbon
Cloth
H+
H2
eX
e-
Electrolyte
Electrode
• Catalyst Utilization: 20 - 30%
Anode: 2H2 Æ 4H+ + 4eCathode: O2 + 4H+ + 4e- Æ 2H2O
Overall : 2H2 + O2 Æ 2H2O
Nanofiber Electrodes by Electrospinning
Spinning nanofibers in high voltage
electric field
Human hair with a nonwoven mat
of electrospun nanofibers in the
background
• Expensive Pt nanoparticles have simultaneous access to
reactants, electrons, and protons
Nanofiber Electrospinning
• Bench-top electrospinning set-up
• NanspiderTM electrospinning machine
Energy-Conversion Nanofibers by Electrospinning
Cell Potential (V)
1.2
Nanofiber Electrodes
Traditional Electrodes
1.0
0.8
0.6
0.4
0.2
0.0
0
300
600
900
1200
-2
Current Density (mA cm )
Pt Catalyst
Conducting
Nanofiber
• Nanofiber-based fuel cell has higher performance than
traditional fuel cell
1500
Other Nanofiber Structures
Solid
Core-Sheath
Hollow
Porous
Core-Sheath, Porous
Hollow, Porous
b) Carbon Nanotube Electrodes
Carbon Nanotubes
• Carbon nanotubes are among the stiffest and strongest materials known, and have
remarkable electronic properties and many other unique characteristics
Carbon Nanotube-Supported Pt
Guo et. al., 2004
• The problem of using carbon nanotubes as Pt support is the lack of effective
method to fabricate carbon nanotube-supported Pt into practical fuel cell
electrodes
Hydroentangling of Carbon Nanotubes
Water Jet
Loose Fibers
Hydroentangled Membrane
Support
• Hydroentangling is a simple, high-speed, low-cost, environment-benign process
for mechanically bonding loose fibers to form a strong and uniform nonwoven
fabric, sheet, or membrane
Hydroentangling of Carbon Nanotubes
Water
• Hydroentangling technology can be used to fabricate carbon nanotubebased macrostructures
Hydroentangled Carbon Nanotubes
200 μm
• The thickness and topology of hydroentangled carbon nanotube structures
can be controlled
Mechanical and Electrical Properties
60
Stress (MPa)
50
Hydroentangled
CNT membrane
40
30
20
CNT buckypaper
10
0
0.0
0.4
0.8
1.2
Strain (%)
CNT buckypaper
0.10
Hydroentangled
CNT membrane
0.05
0.00
0
200
400
Time (s)
600
Conductivity (S/cm)
Creep Strain (%)
0.15
Hydroentangled CNT membrane
102
Hydroentangled CNT-PEO composite
CNT buckypaper
101
CNT buckypaper-PEO composite
100
-50
0
50
100
150
200
Temperature (oC)
• Hydroentangled carbon nanotubes are mechanically strong and highly conducting
Lithium-Ion Batteries
300
Capacity (mAh/g)
Voltage (V)
3
2
1
0
250
200
150
100
50
0
500
1000
1500
Capacity (mAh/g)
2000
Hydroentangled
CNT electrode
PVDF-bound
CNT electrode
0
50
100
150
Current Density (mA/g)
• In addition to fuel cells and batteries, hydroentangling of carbon nanotubes is of
fundamental importance for a broad range of applications, including biocatalysts,
sensors, photonic and electronic micro-devices, hydrogen storage, field emitter
displays, adsorbent materials, and filters, among others
c) Hybrid Electrolyte Membranes
Polymer Electrolyte Membrane Fuel Cells (PEMFCs)
Perfluorosulfonic acid polymers (Nafion®)
CF2 CF2
x
CF2 CF2
y
O
CF2
CF CF3
O
CF2
CF2
SO 3
H
+
x = 5-13.5; y = 1
Haile, Acta Materialia, 2003
• Low operating temperature (< 100 oC)
i) high catalyst loading; ii) CO-poisoning; and iii) difficult heat dissipation
• Poor dimensional stability (80% in liquid water)
Organic-Inorganic Hybrid Membranes
Nanoporous Silica
Functional Polymers
+
+
Good
Dimensional Stability
Hybrid Membrane
+ + +
-- -- - +
High Conductivity
GOALS
High Operating
Temperature
Fuel Cell Performance
H2/O2 Cell
600
Nafion 115
115
Nafion
Porous Silica-PSS
Silica-PSS
Porous
Cell Potential (V)
1.0
0.8
0.6
0.4
0.2
0.0
o
o
o
65
65 CC
130 C
o
130 C
Power Density (mW cm-2)
1.2
500
400
o
300
600
600
900
900
1200
1200
-2
-2
Current Density (mA
(mA cm
cm )
1500
1500
o
65 C
200
100
0
0
o
130 C
300
Nafion 115
Porous Silica-PSS
o
130 C
0
300
600
900
1200
-2
Current Density (mA cm )
• Porous silica-PSS hybrid membrane-based fuel cell has
high potential and power density at 130 oC
1500
Other Hybrid Membrane Structures
• Synthesis
of a novel type of organic-inorganic hybrid
membrane by using SI-ATRP technology to generate extra-high
density, ultra-long functional polymers directly in the nonwoven
pores of electrospun S-ZrO2 nanofiber-based porous
frameworks
d) Neutron Fuel Cell Imaging*
* Collaborated with Prof. Ayman Hawari in the Department of Nuclear Engineering at NCSU
Neutron Imaging Facility at NCSU
• Neutron imaging facility is located at the NCSU PLUSTART reactor
Neutron Fuel Cell Imaging System
• The neutron fuel cell imaging system provides the opportunity to investigate
real-time water distribution in fuel cells under operating conditions
Summary
Fuel Cells (and other systems)
Acknowledgments
Students:
Collaborators:
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Kyung-Hye Jung
Bohyung Kim
Zhan Lin
Liwen Ji
Sudhir Sarma
Edward Arthur Dalton
Barry Roe
Andrew James Medford
Samantha Shintay
Professor Ayman I. Hawari (Nuclear Engineering)
Professor Richard Kotek (Textile Chemistry)
Professor Peter J. Hauser (Textile Chemistry)
Professor Behnam Pourdeyhimi (Nonwoven)
Professor Wendy E. Krause (Textile Engineering)
Professor Peter S. Fedkiw (Chemical Engineering)
Professor Saad A. Khan (Chemical Engineering)
Funding:
• National Science Foundation
• National Textile Center
• Nonwovens Cooperative Research Center
• Institute of Textile Technology
Thank you!
Xiangwu Zhang
919-515-6547
xiangwu_zhang@ncsu.edu