low platinum nanostructured catalysts for fuel cells l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Low-Platinum Nanostructured Catalysts for Fuel Cells PowerPoint Presentation
Download Presentation
Low-Platinum Nanostructured Catalysts for Fuel Cells

Loading in 2 Seconds...

play fullscreen
1 / 18

Low-Platinum Nanostructured Catalysts for Fuel Cells - PowerPoint PPT Presentation


  • 372 Views
  • Uploaded on

Low-Platinum Nanostructured Catalysts for Fuel Cells. Karen Swider-Lyons and Peter Bouwman Naval Research Laboratory Washington, DC Wojtek Dmowski University of Tennessee Knoxville, TN. 14. Source: Transportation Energy Data Book: Edition 19 , DOE/ORNL-6958, September 1999, and

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Low-Platinum Nanostructured Catalysts for Fuel Cells' - daniel_millan


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
low platinum nanostructured catalysts for fuel cells
Low-Platinum Nanostructured Catalysts for Fuel Cells
  • Karen Swider-Lyons and Peter Bouwman
  • Naval Research Laboratory
  • Washington, DC
  • Wojtek Dmowski
  • University of Tennessee
  • Knoxville, TN
slide2

14

Source: Transportation Energy Data Book: Edition 19, DOE/ORNL-6958, September 1999, and

EIA Annual Energy Outlook 2000, DOE/EIA-0383(2000), December 1999

12

Domestic Oil Production

Heavy Trucks

10

GAP

8

Light Trucks

Millions of Barrels per Day

6

Passenger Vehicles

4

2

Automobiles

0

1970

1980

1990

2000

2010

2020

U.S. Transportation Oil Demand

Strategies needed to close the production/utilization gap

Use fuel cells to increase efficiency and decrease fuel consumption

electricity from electrochemistry
Electricity from electrochemistry

H2

H2

1

O2

O2

2

H2O

H2O

H2O

H2O

H2O

Electrochemical conversion process

Oxygen and hydrogen combined on catalysts to produce water, electricity and heat

e-

H2 = 2 H+ + 2 e-

anode

H+

load

Pt catalysts

electrolyte

H+

O2 + 2 H+ + 2 e- = H2O

cathode

H+

Resistive losses due to materials and inefficient reactions.

e-

Proton exchange membrane fuel cell

Perfluorosulfonic acid (Nafion® polymer) membrane

slide4

Hydrocarbons as hydrogen source

S

CH3-(CH2)x-CH3

Gasoline/diesel

  • Logistics fuel
    • Richest source of hydrogen
    • Must be reformed to hydrogen
    • Sulfur, nitrogen and CO2 may be sequestered

Fuel cell

SO2

CO2

H2

H2

H2

H2

H2

H2

H2

OIL

H2

reformer

refinery

Storage tanks

Hydrogen from water electrolysis is expensive due

to high materials and energy costs of electrolyzers

environmental issues with platinum

Environmental Issues with Platinum

Mining Pt creates a lot of waste!

In fuel cell era, attention toward environmentally friendly mining and recycling

From: The Lonmin Group web site

epa advantages of low pt catalysts
EPA Advantages of low Pt catalysts

Lowering Pt will lower the cost of fuel cells

  •  Introduce fuel cells more broadly to consumer market
  •  Lower fuel consumption
  • Less Platinum used
  •  Less Pt mined and recycled
  • Less chemical waste
a possible solution to the problem
A possible solution to the problem
  • Traditional approach
    • Make and test new platinum “alloys”
    • Change catalyst microstructure
  • Our approach
    • Design phase-segregated, mixed conducting nanocomposites for RAPID TRANSPORT of chemical species

Transition metals

?

Alloy compositions

?

nanocomposite phases

Nanocomposite phases are still largely unexplored

-due to difficulty in their characterization?

slide8

Low Pt catalysts for fuel cells

H2O

O2

O

O

O

H+

Pt?

H+

MOx

H+

e-

Nafion

H+

carbon

Pt supported on MOx•H2O supported on carbon

O2 + 4 H+ + 4e-  2 H2O

  • Focus on lowering Pt in fuel cell cathode
  • Cathode has most Pt because
    • slow oxygen reduction kinetics
    • poor Pt stability and ripening over time.

Support Pt on a metal oxide and

improve opportunity for

* proton mobility to Pt sites

* chem/phys attraction of O2

* metal-support interactions with Pt

Catalyst development via

electrochemical and structural analysis

pt mo x systems
Pt-MOx systems
  • 1. Pt-FePOx•xH2O - hydrous iron phosphate
    • Iron phosphate used as an anti-corrosion additive in paint
    • FePOx is a partial oxidation catalyst
    • Under intense scrutiny as a Li-ion battery cathode
  • 2. Pt-SnOx•xH2O - hydrous tin oxide
    • Prior ORR literature shows promise for anhydrous Pt-SnOx
    • Tin hydrates are corrosion resistant

“Open Framework Inorganic Materials”

A. K. Cheetham G. Férey, T. Loiseau,

Angew. Chem. 1999, v. 38 p. 3286.

Example:

Microporous AlPO4

  • Hydrous oxides are excellent for proton conduction
  • Selected oxides have other ideal catalytic properties (e.g. partial oxidation)
  • Materials have open framework structures
pt fepo x vulcan c as orr catalysts
Pt-FePOx/Vulcan C as ORR catalysts
  • Use rotating disk electrode experiments to compare oxygen reduction activity of new catalysts to standard catalysts
  • Critical factors:
  • Electrode preparation
  • & Testing conditions
  • 0.1 M HClO4
  • 1600 rpm
  • 60 °C
  • Compare to
  • theoretical
  • values for Pt

Pt-FePO4 catalysts have higher ORR activity than Pt/carbon standard

9% Pt-FePOx•yH2O + 50% VC

20%Pt-VC

fepo x cyclic voltammetry
FePOx Cyclic Voltammetry
  • FePOx has no activity for the ORR
  • 9 wt %Pt-FePOx is highly active for the ORR

FePOx/VC

9%Pt-FePOx/VC

0.1 M HClO4

1600 rpm

60 °C

structure of pt fepo x electrocatalysts
Structure of Pt-FePOx Electrocatalysts

TEM

Conventional

X-ray diffraction

Structure of the active Pt-FeO

sample is glassy in conventional electron microscopy and X-ray diffraction

atomic pair distribution function pdf
Atomic pair distribution function (PDF)

XRD largely amorphous

Short-range order

PDF

analysis

S(Q)

X-ray or neutron scattering is Fourier-transformed to give distribution of inter-atomic distances in a real space.

High energy, high intensity sources are essential to minimize errors and improve statistics.

slide14
s

Structure of Pt-FePOx with PDF analysis

O

P

Fe

  • PDF analysis of high-energy XRD shows ordered medium
  • range structure
  • Microporous structure facilitates high protonic conduction
  • Pt serves as a glass-modifier and opens pores for access
  • Fe2+/Fe3+ mixed valence states for high catalytic activity
  • Iron phosphate
    • (berlinite) – a-quartz structure
next steps
Next steps…
  • Reduce particle size of oxides to improve electrical properties of FePOx

VC impregnated with Pt-FePOx

Solution-filtered Pt-FePOx

effect of particle size
Effect of particle size
  • Smaller (nano)particle size leads to:
  • Higher electronic conductivity (tunneling from carbon)
  • Higher surface area
  • (more sites for catalysis)

Pt-FePOx mixed with Vulcan carbon

vs. Pt-FePOx impregnated on Vulcan carbon

summary and outlook
Summary and Outlook
  • Fuel cells are efficient fuel conversion systems that may lead to significant fuel savings - less pollution
  • Lower greenhouse gases at a central fuel reforming site and hydrogen stored in fuel tanks
  • Nanomaterials may be useful routes to lowering Pt content of fuel cells and lowering their cost
  • New analytical techniques may be needed for the accurate study of new nanomaterials
acknowledgements
Acknowledgements
  • Department of Energy, EERE
  • Office of Naval Research
  • The synchrotron experiments were carried out at the NSLS - Brookhaven National Lab