A catalytic converter converts poisonous nitrogen oxides and hydrocarbons into nitrogen gas, water, and carbon dioxide by using platinum and rhodium to alter their chemical structure. This is much better for the environment than if the toxins were released into the atmosphere unchanged.
The device itself is a porous, ceramic sponge infused with platinum and rhodium particles. The hydrocarbon and oxygen molecules collide with the platinum particles and are dismantled on the particle's surface. They are then rearranged into water and carbon dioxide. Platinum is an excellent catalyst, and that is its purpose in the catalytic converter. It causes the hydrocarbons to break down faster. According to Louis A. Bloomfield of physicscentral.com, it is such a good catalyst that some hydrocarbons "burn at room temperature in the presence of platinum."
Rhodium, the other catalyst in a catalytic converter, turns nitrogen oxide into nitrogen and oxygen gas. As with platinum and hydrocarbons, the nitrogen oxide collides with the rhodium particles and dissociates into its composite elements. So, in summary, the platinum and rhodium particles cause the hydrocarbons and nitrogen oxide to dissociate into nitrogen and oxygen gas, carbon dioxide, and water, which are relatively harmless when compared with what they used to be. The role of platinum and rhodium is that of a catalyst; they cause the exhaust to dissociate at a faster rate than if they had been released into the atmosphere.
The reactions that take place in a catalytic converter are thus:
The first reaction reduces NO emissions:
2NO=>N2+O2 or 2NO2=>N2+2O2
The second reaction converts carbon monoxide into carbon dioxide:
Catalytic converters are used in all U.S. street-legal automobiles and their application is crucial to the preservation of our atmosphere. They are an excellent example of the science of chemistry positively influencing our environment. If this basic chemistry was applied worldwide, the hazards of global warming would be significantly reduced.