Transcript Intro to Nanocatalysts

U1
Rodrigo Benedetti
Kamal Banjara
Bob DeBorde
John DeLeonardis
What is a Catalyst?
 Changes the rate of a
reaction
 ↑ rate: catalyst
 ↓ rate: inhibitor
 Does not affect
equilibrium
composition
 Neither a product nor
reactant
www.pnl.gov/.../highlights/highlight.asp?id=383
 Often specific to one
reaction
 Can promote one product
if there are competing
reactions
 the catalyst can be
recovered unchanged at
the end of the reaction it
has been used to speed up,
or catalyze.
www.cnms.ornl.gov/nanosci/lp10.sht
m
How do they work?
 Changes activation energy
 Offers an alternative reaction pathway
 New pathway requires less kinetic energy in molecular
collisions
Types of Catalyst
• Catalysts can be either heterogeneous
or homogeneous, depending on
whether a catalyst exists in the same
phase as the substrate
•Other classifications:
Electrocatalyst
Organocatalyst
http://www.bnl.gov/bnlweb/pubaf/pr/photos/2009%5C05%
5CPlatinumCatalyst-300.jpg
Common Examples
 Enzymes
 DNA Polymerase
 Industrial catalysts
 Alumina
 Platinum
www.bionutrisyon.co
m/e-nutrients.html
 Catalytic converter
 Platinum or rhodium
www.allproducts.co
m/.../product4.html
http://maremare1225.wordpress.com/2008/03/31/slee
p-with-one-eye-closed-one-eye-on-catalyticconverter/
2 CO + 2 NO → 2 CO2 +
N2
Intro to Nanocatalysts
http://www.news.cornell.edu/stories/Nov08/nanocatalysts.ws.htm
l
 Definition:
A Nanocatalyst is a substance or material with catalytic properties
that has at least one Nanoscale dimension, either externally or in
terms of internal structures1
 Generally, catalysts that are able to function at atomic scale are
Nanocatalysts
https://www.jyu.fi/fysiikka/en/research/material/compns/research/index_html/supported.j
pg
1http://www.the-infoshop.com/report/bc21463_nanocatalysts.html
Growing interest
 The chart below represents the number of the
publish reports on nanostructured metal catalyst
http://www.bepress.com/cgi/viewcontent.cgi?article=2132&context=ijcre
Specific metal catalyst
Interest in specific elements in the preparation of Nanoparticles in the period 20002007
http://www.bepress.com/cgi/viewcontent.cgi?article=2132&context=ij
cre
Physical properties
 Sizes may varies but can be controlled at
less then 10 nm depending upon the
application
 Particle position can be controlled
increasing the reaction stability and
mechanism
 Controllable exposed atomic structure
 Uniform dispersion
http://news.princeton.edu/uploads/243/image/nanocatalyst_diagram.j
pg
http://www.htigrp.com/data/upfiles/pdf/Nanocatalysts0304.p
df
Chemical Properties
 Catalytic activity
 Stability
http://www.tacc.utexas.edu/research/users/features/stefano.php
Catalytic Activity
 Very important factor in choosing a nanocatalyst
 Porous nanostructure provides high surface to volume ratio hence
increase the catalytic activity1
 Example : in a Direct Formic Acid Fuel Cells, CO poisoning
significantly limits the catalytic activities of Pt/Ru and Pt/Pd alloys
for formic acid oxidation
 Solution to the Poisoning ; Decoding the nano particles with carbon
support2
1Nanocatalyst
http://tinyurl.com/yzqps4
d
fabrication and the production of hydrogen by using photon energy; ming –Tsang Lee, David J. Hwang, Ralph Greif
and Costas P Gigoropoulous
2References:
Performance characterization of Pd/C nanocatalyst for direct formic acid fuel cells; S.HA, R. Larsen and R.I. Masel
Stability
 Most notable property
 Stability helps in achieving
desire size nanopartilces with
uniform dispersion on the
substrate like carbon
 Nanocalatyst like Pt can be
stabilize by stabilizing agents
like surfactants, ligands or
polymers
http://www.natureasia.com/asia-materials/article_images/425.jpg
Effect of temperature and pressure
on the Nanocatalysts
 Melting point may lower from the original
metal species
- For example: platinum has melting point is
around 2000K but the nano catalyst made up
of Pt has melting point around 1000K
 Change in melting point have both pros
-
-
and cons
Pros
Possibility of using these Nanocatalysts in
liquid phase
In case of fuel cells it may penetrate through
the layers to increase the surface area of
reaction
Cons
May not be useful in some reactions
Durability may change as it might reduce the
adherence capability to substrate
References: Dr. Balbuena; Chemical Engineering professor at
TAMU
http://www.ufz.de/index.php?en=5979
Advantages of Nanocatalyst
 These advantages are
related to the inherent
properties of the
material.
 Also to their:
 Size
 Charge
http://www.inano.au.dk/research/research-areas/nanoenergy-materials/nanocatalysis/
 Surface area
Size and surface area
 Nanocatalyst can fit where
many of the traditional
catalyst will not.
 By nanocatalyst being very
chemistry.brown.edu/research/sun/research.html
http://www.bnl.gov/bnlweb/pubaf/pr/photos/2002/nanoparticlesw.jpg
small in size, this property
creates a very high surface to
volume ratio. This increase
the performance of the
catalyst since there is more
surface to react with the
reactants
Charge
 Some Nanocatalyst can develop partials and
net charges that help in the process of making
and braking bonds at a more efficient scale.
Nano-catalysts are part of
tomorrow’s cutting edge
technology.
 One example is the use of Hydrogen as a
domestic fuel.
As you may know, Hydrogen is as abundant
as it is environmentally friendly. Companies
would love to develop an efficient Hydrogen
Fuel cell that is financially feasible.
A typical Hydrogen fuel
cell1.
 One major problem however, is the method
of reversible storage of Hydrogen. One
company, HRL Laboratories, is currently
working on a multi-million dollar project
that will increase the efficiency of current
Hydrogen storage methods by utilizing the
properties of Nano-catalysts.
Imagine filling up your tank
with a gas instead of liquid2.
The next slide shows the project overview
HRL Laboratories are working hard
to meet and exceed Department of
Energy standards for hydrogen
storage.
http://www.hydrogen.energy.gov/pdfs/review06/st_16_olson.p
df
Hydride Destabilization Cycle
•The system cycles between Hydrogencontaining alloy and a stabilized-alloy
state.
•There is a lower ∆H for the stabilized alloy
(where Hydrogen is destabilized).
•The alloy allows for Hydrogen to become
released at a lower temperature and energy
level.
•Nano-catalysts decrease the diffusion
distance resulting in fast exchange rates
making the whole process more efficient.
•Nano-catalysts also can act as a scaffold
for the metal hydride, allowing structuredirected agents as well as deterring particle
conglomeration.
http://www.hydrogen.energy.gov/pdfs/review06/st_16_olson.p
df
8.
3.
4.
7.
With Nano-catalysts, many
companies are on the verge of
breaking through the Hydrocarbon
age and transforming how we
imagine energy and fuel for domestic
as well as industrial purposes.
5.
6.
Pictures cited
1.http://www.ngdir.org/SiteLinks/Kids/html/energy_mfahem_%20%20HYDROGEN.html.ht
m
2. http://www.fastfocus.tv/Media.aspx?id=18
3. http://www.casfcc.org/2/StationaryFuelCells/WhyFuelCells.aspx
4. http://www.netl.doe.gov/technologies/coalpower/fuelcells/seca.html
5. http://www.hydrogenics.com
6. http://www.hydrogendiscoveries.com/index.html
7. http://energiatechnologies.com/contact.asp
8. http://www.h2fc.com/Newsletter/Companies/PRs/axane_041504.html
Sources
 Wikipedia.org
 http://www.htigrp.com/data/upfiles/pdf/Nanocatalysts030
4.pdf
 http://www.theinfoshop.com/report/bc21463_nanocatalysts.html
 Faculty member: Dr. Perla B. Balbuena