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

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. 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 5CPlatinumCatalyst-300.jpg

Common Examples Enzymes DNA Polymerase Industrial catalysts Alumina Platinum Catalytic converter Platinum or rhodium 2 CO + 2 NO → 2 CO 2 + N 2 m/e-nutrients.html m/.../product4.html p-with-one-eye-closed-one-eye-on-catalytic- converter/

Intro to Nanocatalysts 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 structures 1 Generally, catalysts that are able to function at atomic scale are Nanocatalysts pg

Growing interest The chart below represents the number of the publish reports on nanostructured metal catalyst

Specific metal catalyst Interest in specific elements in the preparation of Nanoparticles in the period 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 df pg

Chemical Properties Catalytic activity Stability

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 d

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

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

Advantages of Nanocatalyst These advantages are related to the inherent properties of the material. Also to their: Size Charge Surface area 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 w.jpg

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. 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 1. Imagine filling up your tank with a gas instead of liquid 2.

HRL Laboratories are working hard to meet and exceed Department of Energy standards for hydrogen storage. df

Hydride Destabilization Cycle The system cycles between Hydrogen- containing 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 structure- directed agents as well as deterring particle conglomeration. df

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

Pictures cited 1. m

Sources Wikipedia.org 4.pdf 4.pdf infoshop.com/report/bc21463_nanocatalysts.html infoshop.com/report/bc21463_nanocatalysts.html Faculty member: Dr. Perla B. Balbuena