TY - JOUR T1 - Electronic decoupling of surface layers from bulk and its influence in oxidation catalysis: a molecular beam study JF - Applied Surface Science Y1 - 2009 A1 - Thirunavukkarasu, Kandasamy A1 - Nagarajan, Sankaranarayanan A1 - Gopinath, Chinnakonda S. KW - Electronic decoupling KW - heterogeneous catalysis KW - molecular beam KW - Oxidation KW - Pd(111) KW - Subsurface diffusion AB -

Interactions between oxygen and Pd-surfaces have important implications, especially towards oxidation reactions, and influence of subsurface oxygen to oxidation reactions is the focus of the present study. In our efforts to understand the above aspects, CO oxidation reactions have been carried out with mixed molecular beam (MB), consisting CO and O(2), on Pd(1 1 1) surfaces under a wide variety of conditions (T = 400-900 K, CO: O(2) = 7: 1 to 1: 10). A new aspect of the above reaction observed in the transient kinetics regime is the evidence for oxygen diffusion into Pd subsurface layers, and its significant influence towards CO oxidation at high temperatures (>= 600 K). Interesting information derived from the above studies is the necessity to fill up the subsurface layers with oxygen atoms to a threshold coverage (theta(O-sub)), above which the reactive CO adsorption occurs on the surface and simultaneous CO(2) production begins. There is also a significant time delay (G) observed between the onset of oxygen adsorption and CO adsorption (and CO(2) production). Above studies suggest an electronic decoupling of oxygen covered surface and subsurface layers, which is slightly oxidized, from the metallic bulk, which induces CO adsorption at high temperatures and simultaneous oxidation to CO(2). (C) 2009 Elsevier B.V. All rights reserved.

PB - Inst Phys; Indian Assoc Cutivat Sci CY - PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS VL - 256 IS - 2 N1 - 2nd International Conference on Physics at Surfaces and Interfaces (PSI2009), Puri, INDIA, FEB 23-27, 2009 U3 - Foreign U4 - 1.793 ER -