Coadsorbate effects in surface photochemistry: Bimolecular reactions and photodesorption yield enhancement for NO coadsorbed with O-2 on Pt(111)

[摘要] A study of the surface chemistry of coadsorbed NO and O-2 on Pt(111) using electron energy loss spectroscopy (EELS), temperature programmed desorption (TPD), and photon induced desorption spectroscopy (PID) is presented. A (NO)-N-14-O-18 isotope exchange reaction product is detected in TPD of (NO)-N-14-O-16/O-18(2)/Pt(111) with the primary desorption peak occurring at 315 K. The wavelength dependence of photodesorption of (NO)-N-14-O-18, (NO)-N-14-O-16, and O-2 from (NO)-N-14-O-16/O-18(2)/Pt(111) at 85 K with photons between 240 and 950 nm was measured, with that of (NO)-N-14-O-18 found to be very similar to O-2 photodesorption. EELS features at 95 meV (delta(ONO)] and 155 meV (nu(s)(ONO)] reveal the production of NO2 upon NO adsorption on O-2/Pt(111) at 90 K. A new adsorption state of NO, denoted gamma NO, formed upon coadsorption of NO with O-2 on Pt(111) was characterized by a unique vibrational signature in EELS [nu(gamma)(N-O)=236 meV]. gamma NO was found to have a photodesorption cross section approximately 4000 times greater than that of NO adsorbed alone on clean Pt(111) due to photoyield enhancement by coadsorbed O-2, while exhibiting a similar wavelength dependence to NO/Pt(111).

[发布日期] 1996-07-01

[关键词] electron energy loss spectroscopy;low index single crystal surfaces;nitrogen oxides;oxygen;photochemistry;photon stimulated desorption (PSD);platinum;surface photochemistry