Nanocatalysts - Nanotechnology - Lecture Slides, Slides of Nanotechnology

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U

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=

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

Intro

to

Nanocatalysts

http://www.news.cornell.edu/stories/Nov08/nanocatalysts.ws.html

 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 structures 1  Generally, catalysts that are able to function at atomic scale are Nanocatalysts 1 http://www.the ‐infoshop.com/report/bc21463_nanocatalysts.html https://www.jyu.fi/fysiikka/en/research/material/compns/research/index_html/supported.jpg

Specific

metal

catalyst

Interest in specific elements in the preparation of Nanoparticles in the period 2000 ‐ 2007 http://www.bepress.com/cgi/viewcontent.cgi?article=2132&context=ijcre

Physical

properties

 Sizes may varies but can be controlled at less then

nm depending upon the application  Particle position can be controlled increasing the reaction stability and mechanism  Controllable exposed atomic structure  Uniform dispersion http://www.htigrp.com/data/upfiles/pdf/Nanocatalysts0304.pdf http://news.princeton.edu/uploads/243/image/nanocatalyst_diagram.jpg

Catalytic Activity  Very important factor in choosing a nanocatalyst  Porous nanostructure provides high surface to volume ratio hence increase the catalytic activity 1  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 support 2 2 References: Performance characterization of Pd/C nanocatalyst for direct formic acid fuel cells; S.HA, R. Larsen and R.I. Masel 1 Nanocatalyst fabrication and the production of hydrogen by using photon energy; ming –Tsang Lee, David J. Hwang, Ralph Greif and Costas P Gigoropoulous http://tinyurl.com/yzqps4d

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

Advantages

of

Nanocatalyst

 These advantages are related to the inherent properties of the material.  Also to their:  Size  Charge  Surface area http://www.inano.au.dk/research/research ‐areas/nano ‐ energy ‐materials/nanocatalysis/

Size

and

surface

area

 Nanocatalyst can fit where many of the traditional catalyst will not.  By nanocatalyst being very 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 chemistry.brown.edu/research/sun/research.html http://www.bnl.gov/bnlweb/pubaf/pr/photos/2002/nanoparticles ‐ w.jpg

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.  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. The next slide shows the project overview A typical Hydrogen fuel cell

Imagine filling up your tank with a gas instead of liquid

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.pdf