The Role of Carbon Deposition from CO Dissociation on Platinum Crystal Surfaces during Catalytic CO Oxidation: Effects on Turnover Rate, Ignition Temperature, and Vibrational Spectra

Abstract

Experiments were performed to understand the process of ignition during platinum catalyzed CO oxidation using sum frequency generation (SFG) vibrational spectroscopy, Auger electron spectroscopy (AES), gas chromatography (GC), and temperature programmed desorption (TPD). Both CO dissociation and CO oxidation ignition studies on the (100), stepped (557), and (111) surfaces of platinum are presented. Rapid CO dissociation on the Pt(100), Pt(557), and Pt(111) occurred in narrow temperature ranges (±10 K) at 500, 548, and 673 K, respectively. The CO ignition temperature at a pressure of 40 Torr of CO and 100 Torr of O2 is lower on Pt(100) than on Pt(111) and Pt(557). Thus, both CO dissociation and the ignition of CO oxidation are structure sensitive. An in depth study of CO oxidation on Pt(557) was performed on both initially clean and initially carbon covered platinum surfaces to investigate the role of carbon obtained from CO dissociation in CO oxidation. Under excess O2 and excess CO conditions, a clean pl...