Evidence for an oxygen intermediate in the catalytic reduction of NO by CO on rhodium surfaces

Evidence for an oxygen intermediate in the reaction of NO and CO to form N2 and CO2 over rhodium surfaces is presented. High resolution electron energy loss spectroscopy (ELS) measurements indicate that both NO and CO molecules associatively adsorb on the Rh(331) single crystal surface at 300 K. Chemisorbed NO readily dissociates on this surface upon heating at 450 K. At 700 K high resolution ELS and Auger electron spectroscopy (AES) both indicate that only oxygen is present on the catalyst surface. N2 desorption below this temperature is easily detected by mass spectroscopy. The addition of CO to this surface oxygen at 700 K results in the formation of gaseous CO2 and the removal of the surface oxygen species. Similar results were obtained when O2 was substituted for NO as a control indicating that oxygen is indeed a surface intermediate under our experimental conditions. (Author)