Kinetics of PdO formation and CO reduction on Pd(110)

Recent studies have identified the 'subsurface' oxygen on Pd(110) as a nucl eation of an oxide phase. This species has been postulated as responsible f or oscillations in the catalytic CO oxidation on this surface. We have inve stigated the kinetics of this oxide formation and its reduction by CO on Pd (110) at temperatures and pressures where oscillations occur, using tempera ture-programmed desorption and X-ray photoelectron spectroscopy. The rate o r oxide reduction measured was found to agree approximately with previously measured values for chemisorbed oxygen, indicating that the oxide species are weakly bound or unstable, However, we find significant qualitative and quantitative differences in the kinetics of oxide formation and other mecha nisms assumed in previous studies. (C) 2000 Elsevier Science B,V, All right s reserved.