If your exhaust system and catalytic converter has become clogged with carbon deposits then yes adding a bottle of Seafoam fuel additive to your gasoline tank can help clean the carbon off your engines components as well as the catalytic converter.
The seafoam is a wonderful product to help keep your fuel injectors clean as well so you'll clean the exhaust system, catalytic converter and the fuel system as well.
I would also recommend every other fill up or at least every 6 months or once per year to add a bottle of catalytic converter cleaner to the gas tank.
The catalytic converter cleaner will do a much better job at cleaning the catalytic converter than the Seafoam but the seafoam will also help.