a catalyst for the combination of co and o 2 to form co 2 which includes a platinum group metal -- e . g ., platinum ; a reducible metal oxide having multiple valence states -- e . g ., sno 2 ; and a compound which can bind water to its structure -- e . g ., silica gel . this catalyst is ideally suited for application to high - powered , pulsed , co 2 lasers operating in a sealed or closed - cycle condition .