[EvilFrog (OP)]

what is catalytic converter? what is Pd/Pt/Rh catalyst? []

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what is catalytic converter? what is Pd/Pt/Rh catalyst? []

It's a device which serves essentially 3 things:
1. To clean exaust combustion gases and so decrease air pollution (ok) [].
2. Increase the veichle's consumptions and decrease the performances, so one has to pay more for fuel (bad) [].
3. Make people who buy a new car pay more taxes (because of the reduced performances and increased consumptions) than those who owns an old, super-pollutant veichle (bad) [].

Take your own conclusions...

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Anyway, a catalytic converter it's essentially a pipe (the main one, because there are also pre-converters) which has an internal honeycomb structure, made of ceramic material, on the surface of which are layered precious metals (those you wrote) which catalyze various reactions, the most important are (not balanced):
1. NOx --> N₂ + O₂
2. HC + O₂ -->H₂O + CO₂
3. CO + O₂ --> CO₂

What I don't understand is this: since metallic catalytic converter (instead of ceramic) are much more efficient in expelling the gas and so in not dropping down performances, why the heck they don't put them in the firm? []
http://en.wikipedia.org/wiki/Catalytic_converter

[EvilFrog (OP)]

Ha ha! You are right! WHY DON'T DO LIKE THIS? Anyway, thank you for your answer. []