Effects of pretreatment conditions on a Pt/SnO2 catalyst for the oxidation of CO in C02 lasers

CO oxidation catalysts are important for long-life closed-cycle operation of CO{sub 2} lasers. The electrical discharges frequently used to excite such lasers decompose some CO{sub 2} to CO and O{sub 2} but many of their applications, including remote sensing from space vehicles, prohibit addition of makeup gas or removal of decomposition products because of volume and weight constraints. These lasers thus represent a new and important application for low-temperature CO oxidation catalysts, since for space applications, no catalyst heating is allowed to minimize power consumption. The most promising catalysts whose performance has been verified by actual laser operation consist of Pt and/or Pd on tin(IV) oxide. This paper presents results of a study of various pretreatment techniques on the activity of a commercially available Pt/SnO{sub 2} catalyst. Pretreatment with the reducing gases, CO and H{sub 2}, produces approximately equal steady-state CO{sub 2} yields which are significantly higher than those for the other pretreatment gases, although the steady-state is more rapidly attained with the H{sub 2} pretreatment. Pretreatment with O{sub 2} in He results in only slightly greater CO{sub 2} yields than pretreatment with He alone.