I've seen many mentions of metal catalysts why metal? What do they do?

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In summary, during a chemical reaction, catalysts are substances that speed up the reaction by lowering the activation energy. Metals are commonly used in catalysis because of their high surface energy, which allows for reactive surfaces where reactions can occur. Different metals have different surface energies and can have varying degrees of effectiveness in different reactions. While ceramics, such as alumina, can also be used as catalysts, polymers are not suitable due to their lower surface energy and lack of dangling bonds on their surfaces.
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pa5tabear
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I know a catalyst is something that speeds up a reaction, usually by lowering the activation energy, by adding intermediate steps, which are not so "high energy".

Why metal? What are they doing in the reaction? For example, I've seen platinum mentioned a lot, or also nickel. Do these two have something special? Could any metals be used?

Here's an example:

http://phys.org/news/2012-09-scientists-mechanism-water-splitting-catalysts.html
 
Chemistry news on Phys.org
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here's what I think happens:

they provide a reactive surface for reactions to take place on because they have a relatively high surface energy - the atoms at the surface of a metal have dangling bonds, so to speak (are not bonded in the typical unit cell for the metal) and are less energetically favorable in that configuration than atoms on the interior.

When something like, say, a gas molecule, adheres to the surface, the high surface energy means that it might be more favorable for the gas, especially at high temperature, to break up into atoms that bond (temporarily) to the surface. But since diffusion is sped up at high temperatures, these atoms can also move around on the surface and if they meet another atom that they can form a covalent bond with, they'll form that bond and then diffuse away from the metal. Doesn't happen for all atoms, of course, otherwise there'd be a 100% yield. However, it does happen for a large fraction of them.

Different metals have different surface energies, so it might depend on the specific reaction.

Ceramics are also used for catalysis. Alumina, for example. Same principle; the ions at the surface of a ceramic are not part of a complete unit cell and thus are "left dangling". However some ceramics are totally inert, so I think it might have to do with the identity of the ions.

Why not say... polymers? Polymers are molecular solids; their surfaces have no dangling bonds because they are molecular solids, have lower surface energy and thus can't break things apart.
 

1. What is a metal catalyst?

A metal catalyst is a substance, usually a metal or metal compound, that speeds up a chemical reaction without being consumed in the process. It works by lowering the activation energy required for the reaction to occur, making the reaction happen more quickly and efficiently.

2. Why are metal catalysts commonly used?

Metal catalysts are commonly used because they are highly effective at increasing the rate of chemical reactions. They are also abundant, relatively inexpensive, and can be easily manipulated to control the reaction conditions. Additionally, metal catalysts often have high selectivity, meaning they can target specific reactions and produce desired products without creating unwanted byproducts.

3. What types of reactions do metal catalysts typically catalyze?

Metal catalysts can catalyze a wide range of reactions, including oxidation, reduction, hydrogenation, and polymerization. They are also commonly used in industrial processes, such as in the production of fuels and chemicals.

4. How do metal catalysts work?

Metal catalysts work by providing an alternative pathway for a reaction to occur, known as the catalytic cycle. This involves the catalyst interacting with the reactants to form an intermediate complex, which then breaks down to form the desired products. The catalyst then regenerates, ready to repeat the cycle and catalyze more reactions.

5. Are there any drawbacks to using metal catalysts?

While metal catalysts are highly effective, they can also have some drawbacks. They may be toxic or corrosive, and they can also be sensitive to impurities or changes in reaction conditions. Additionally, some metal catalysts may be expensive or require specialized equipment for their use. Careful consideration must be taken when selecting and using metal catalysts in order to achieve the desired results.

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