A402 144
Surface Science 146 (1984} 144 154 North-flolland, Amsterdam
T H E R M A L STABILITY OF A D S O R B E D C H j N C O O N C u { l l 0 } Pt( 110} F R O M V I B R A T I O N A L A N D P H O T O E L E C T R O N SPECTROSCOPIES Mark S U R M A N , F. SOLYMOSI *, Renee D. D I E H L * * Peter HOFMANN *** a n d D a v i d A. K I N G
AND
The Donnan Lahoratorte.~, The Unn,epwttv oJ l.i~'epT~ool, P.O. Bo~ 147. l.i~,e~7too/ l.t'~) 3BX. UK Received L5 August 1983; accepted for publication 12 June 1984 The thermal stability of C H j N C O adsorbed on C u { l l 0 } and P t { l l 0 } is investigated using HREELS, TPD, and ARUPS. C t t j N C O desorbs largely without fragmentation from C u { l l 0 } . but on P t { l l 0 } only about 20'~: of the adsorbed C H j N C O desorbs intact, with 80q~ decomposing on the surface at T > 200 K into CO(a), H(a), C t t d a ) , N(a) and Ntt,,(a) fragments. The kinetics of the surface decomposition were characterised for 220 < 1"< 300 K by H R EELS and the activation energy for C H j N C O decomposition was found to vary strongly as a function of coverage,
Surface Science 146 (1984) 155 178 North-Holland, Amsterdam
155
CO O X I D A T I O N O N Pd(100): A S T U D Y OF THE C O A D S O R P T I O N OF OXYGEN AND CARBON MONOXIDE E.M. S T U V E a n d R.J. M A D I X Dq~artr*wnt o/ ('heroical t:'ngineerlng, ,~'tat~[~)rd ~jnil,ers~tl'. Nta~/ord. (ah/i)rnla o4.'}0.',, U~'/|
and
C.R. B R U N D L E I B M Re~earch Laboratories, San Jose, ('al@>rnta 95l~)3, USA Received 20 March 1984; accepted for publication 12 June 1984 Oxygen adsorption, and coadsorption and reaction with CO were studied with temperature programmed reaction spectroscopy (TPRS), low energy electron diffraction (LEED), and high resolution electron energy loss spectroscopy (EELS). Oxygen adsorption at 300 K was studied for coverages up to 0.5, while coadsorption with CO was studied in the temperature range of 80 to 450 K, and O and CO coverages of 0 to 0.25 and 0 to 0.8, respectively. Oxygen adsorbed into p(2 × 2) islands for coverages in excess of 0.05 and yielded a full,,' developed p(2 × 2) structure for 1 / 4 monolayer coverage at 300 K. The p ( 2 × 2 ) O pattern was gradually replaced by a c ( 2 × 2 ) O structure as the oxygen coverage was increased to 0.5. Oxygen desorption occurred in three temperature programmed desorption states at 840, 730, and 695 K. The highest temperature state was populated at all coverages, whereas the 730 and 695 K states appeared as the oxygen coverage exceeded 0.25 and 0.36, respectively. The 695 K state was unusually narrow suggesting attractive interactions in the oxygen adlayer for coverages of 0.36 to 0.5. For the surface precovered with 0.25 monolayer of oxygen, CO adsorption at 80 K caused a disordering of the p(2 × 2)0 structure. At lower oxygen coverages CO initially adsorbed at sites apart from the oxygen domains, but also adsorbed within oxygen islands upon filling of the exterior sites. CO adsorption in the interior of the islar/ds produced a directly interacting CO Pd O complex characterized by a CO stretching