Nanoscience and nanotechnology for advanced energy systems

1
Nanoscience and nanotechnology for advanced
energy systems
Two uses of NS and NT for advanced energy
systems

• Make non-sustainable systems more effective,
  cleaner, and less expensive (short-term)
• Develop more efficient and sustainable energy
  systems (long-term)

NS and NT can impact three broad areas

• Light Harvesting
• Catalysis
• Materials

2
Energy Systems

• Energy sources
• Energy storage
• Energy conversion
• Energy use
• Emission cleaning

3
Energy Sources

• Non-sustainable sources
• Oil
• Natural Gas
• Coal
• Nuclear
• Sustainable sources
• Photovoltaics (PV)
• Solar thermal
• Solar hydrogen
• Wind
• Hydo
• Biomass
• Geothermal

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Impact of NS and NT on Energy Sources
Energy Sources NS and NT aspects
Renewable and/or unlimited
PV Solar thermal Solar hydrogen Wind Wave Hydro Biomass Geothermal LH, M M LH, C, M M M M C Sensors, M
Nonrenewable
Oil Natural Gas Coal C, M, sensors C C

• Light Harvesting (LH)
• Catalysis (C)
• Materials (M)

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Impact of NS and NT on Energy Storage
Energy Storage NS and NT aspects
Water dams M
Pneumatic M
Hydrogen storage M, C, kinetics
Batteries M
Supercapacitors M, nanolayered structures, electrolytes

• Light Harvesting (LH)
• Catalysis (C)
• Materials (M)

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Impact of NS and NT on Energy Conversion
Energy Conversion NS and NT aspects
Combustion Engines M, diagnostics
Turbines M, diagnostics
Fuel Cells C, diagnostics, electrolytes
Magneto-hydrodynamic generators M
Thermo/piezoelectric materials M, nanolayered structures

• Light Harvesting (LH)
• Catalysis (C)
• Materials (M)

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Impact of NS and NT on Energy Use and Emission
Cleansing
Energy Use NS and NT aspects
Industrial/mining Sensors, phase separation
Residential Non-thermal lighting, M
Transportation M
Emission Cleaning
Gas/Air C
Water C

• Light Harvesting (LH)
• Catalysis (C)
• Materials (M)

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Materials
Nanoscience enables precise control of materials
structures, enabling enhanced material
properties

• Lighter
• Improved gas mileage
• Stronger
• Higher sustainable wind speeds (windmills)
• Higher allowable operating temperature
• Thermal power generation
• Corrosion resistance
• Longer service life in aggressive environment
  (mining, machining, etc.)
• Adjustable material properties
• Smart windows for efficient heating/cooling

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Piezoelectric materials for energy harvesting
Piezoelectric Materials

• Enables conversion of mechanical to electrical
  energy
• Electrical polarization upon uniform mechanical
  stimulus
• Harvest the energy from vibration or disturbance
  originating from footsteps, heartbeats, ambient
  noise and air flow

Dramatic enhancement in energy harvesting for a
narrow range of dimensions in piezoelectric
nanostructures Physical Review B (Condensed
Matter and Materials Physics), v 78, n 12, 15
Sept. 2008, p 121407

• Tailored nanostructures of lean zirconate
  titanate (PZT) with specific dimensions for
  increased energy scavenging capability

Nanowire piezoelectric nanogenerators on plastic
substrates as flexible power sources for
nanodevices Advanced Materials, v 19, n 1, Jan 8,
2007, p 67-72

• Arrays of piezoelectric, semiconducting ZnO
  nanowires (NW) grown on flexible plastic
  substrates can be used to convert mechanical
  energy into electrical energy using a conductive
  atomic force microscope

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Piezoelectric materials
Synthetic Ceramics

• barium titanate (BaTiO3)Barium titanate was the
  first piezoelectric ceramic discovered.
• lead titanate (PbTiO3)
• lead zirconate titanate (PZT) most commonly used
  piezo material
• potassium niobate (KNbO3)
• lithium niobate (LiNbO3)
• lithium tantalate (LiTaO3)
• sodium tungstate (Na2WO3)
• Ba2NaNb5O5
• Pb2KNb5O15

Crystals - mainly quartz Polymers
Polyvinylidene fluoride (PVDF)
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The new field of nanopiezotronics
Materials Today, v 10, n 5, May 2007, p 20-8
(a) Scanning electron microscopy (SEM) images of
aligned ZnO NWs grown on an a-Al2O3 substrate.
(b) Experimental setup for generating electricity
through the deformation of a semiconducting and
piezoelectric NW using a conductive AFM tip. The
root of the NW is grounded and an external load
of RL 500 MW is applied, which is much larger
than the inner resistance RI of the NW. The AFM
tip is scanned across the NW array in contact
mode. (c) Output voltage image obtained when the
AFM tip scans across the NW array.
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Microfibrenanowire hybrid structure for energy
scavenging
Nature 451, 809-813 (14 February 2008)

• Simple, low-cost approach that converts
  low-frequency vibration/friction energy into
  electricity using piezoelectric zinc oxide
  nanowires grown radially around textile fibres

a, An SEM image of a Kevlar fibre covered with
ZnO nanowire arrays along the radial direction.
b, Higher magnification SEM image and a
cross-section image (inset) of the fibre, showing
the distribution of nanowires. c, Diagram showing
the cross-sectional structure of the
TEOS-enhanced fibre, designed for improved
mechanical performance. d, SEM image of a looped
fibre, showing the flexibility and strong binding
of the nanowire layer. e, Enlarged section of the
looped fibre, showing the distribution of the ZnO
nanowires at the bending area.
ZnO fibers grown using hydrothermal approach
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Microfibrenanowire hybrid structure for energy
scavenging - fiber-based generator
a, Schematic experimental set-up of the
fibre-based nanogenerator. b, An optical
micrograph of a pair of entangled fibres, one of
which is coated with Au (in darker contrast).
c, SEM image at the 'teeth-to-teeth' interface
of two fibres covered by nanowires (NWs), with
the top one coated with Au. The Au-coated
nanowires at the top serve as the conductive
'tips' that deflect/bend the nanowires at the
bottom. d, Schematic illustration of the
teeth-to-teeth contact between the two fibres
covered by nanowires. e, The piezoelectric
potential created across nanowires I and II under
the pulling of the top fibre by an external
force. The side with positive piezoelectric
potential does not allow the flow of current
owing to the existence of a reverse-biased
Schottky barrier. Once the nanowire is pushed to
bend far enough to reach the other Au-coated
nanowire, electrons in the external circuit will
be driven to flow through the uncoated nanowire
due to the forward-biased Schottky barrier at the
interface. f, When the top fibre is further
pulled, the Au-coated nanowires may scrub across
the uncoated nanowires. Once the two types of
nanowires are in final contact, at the last
moment, the interface is a forward biased
Schottky, resulting in further output of electric
current, as indicated by arrowheads. The output
current is the sum of all the contributions from
all of the nanowires, while the output voltage is
determined by one nanowire.
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Heterogeneous Catalysts
Catalysts save energy by

• Reducing operating temperature at which chemical
  reactions occur
• Improve selectivity towards most valuable product

Heterogeneous Catalysis - catalyst in different
phase than reactants

• Fabrication of catalytic materials with high
  surface-to-volume ratio
• Precise control of size, shape, and chemistry

Recent catalyst research
High surface area niobium oxides as catalysts for
improved hydrogen sorption properties of ball
milled MgH2 Journal of Alloys and Compounds, v
460, n 1-2, 28 July 2008, p 507-12
Nanostructured platinum catalyst layer prepared
by pulsed electrodeposition for use in PEM fuel
cells International Journal of Hydrogen Energy, v
33, n 20, October, 2008, p 5672-5677
Ordered silicon nanocones as a highly efficient
platinum catalyst support for direct methanol
fuel cells Journal of Power Sources, v 182, n 2,
1 Aug. 2008, p 510-14
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"Hairy Foam" Carbon nanofibers grown on solid
carbon foam. A fully accessible, high surface
area, graphitic catalyst support (Journal of
Materials Chemistry, v 18, n 21, , 2008, p
2426-2436)
Fig. 7 SEM micrographs of different types of CNF
coverage of the RVC after 5 h of CNF synthesis at
773 K using ethylene as the carbon source.
Fig. 8 SEM micrographs showing the CNF layer
thickness
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Planar Model Catalysts
Planar model catalysts (PMC) model catalytic
systems with specific size and shape, deposited
on planar substrates

• Easier to model than random structure of
  real-life catalysts allowing for for detailed
  characterization
• Fabrication of catalytic materials with high
  surface-to-volume ratio
• Precise control of size, shape, and chemistry

Recent PMC research
CO adsorption energy on planar Au/TiO2 model
catalysts under catalytically relevant
conditions Journal of Catalysis, v 252, n 2, Dec
10, 2007, p 171-177
A novel approach for measuring catalytic activity
of planar model catalysts in the polymer
electrolyte fuel cell environment Journal of the
Electrochemical Society, v 153, n 4, April, 2006,
p A724-A730
Lithographically defined Pt disks
Carbon monoxide oxidation over well-defined
Pt/ZrO2 model catalysts Bridging the material
gap Applied Surface Science, v 253, n 3, 30 Nov.
2006, p 1310-22
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Pd-Alumina PMCs
The model catalysts are characterized with
respect to their structure using various
techniques

• Low energy electron diffraction (LEED)
• Scanning tunnelling microscopy (STM)
• Auger electron spectroscopy (AES)
• X-ray photoelectron spectroscopy (XPS)
• The interaction with gas molecules is examined
  using
• Thermal desorption spectroscopy (TDS)
• Sum frequency generation (SFG)
• Polarization-modulation infrared reflection
  absorption spectroscopy (PM-IRAS)

Schematic illustration and STM image of a
Pd-Al2O3 model catalyst.
Annual Reports on the Progress of Chemistry,
Section C (Physical Chemistry), 100 (2004) 237 or
Physical Chemistry Chemical Physics, 3 (2001) 4621
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Nanoparticle Catalysts
Nanoparticle catalysts

• Materials can exhibit significantly different
  reactivity at nanoscale
• Bulk gold inert
• Gold nanoparticle highly active catalyst

Novel Fe-Ni nanoparticle catalyst for the
production of CO- and CO2-free H2 and carbon
nanotubes by dehydrogenation of methane Applied
Catalysis A General, v 351, n 1, Dec 15, 2008, p
102-110
Biodiesel process uses nanoparticle
catalyst Industrial Bioprocessing, v 28, n 7,
July, 2006, p 2
Au-Ag alloy nanoparticle as catalyst for CO
oxidation Effect of Si/Al ratio of mesoporous
support Journal of Catalysis, v 237, n 1, Jan 1,
2006, p 197-206