Thermal and Photon Driven Reactions of NO and H2O Adsorbed on Graphite

Abstract: The topic of this thesis is the interaction of water (H2O) and nitric oxide (NO) with the graphite (C(0001)) surface. Specifically the effects of coadsorbing metals (Na, Ag) and subjecting the adsorption systems to thermal and photon activation were studied. When coadsorbing sodium and water a critical coverage was found, θc, above which dissociative adsorption took place. For coverages below θc the adsorption was molecular and resulted in clustering of the molecules around the Na. The reaction products from the NO/Na/graphite system were shown to depend on the ratio between adsorbed NO and Na, with three distinct coverage ratio regimes. When water was added to the system small amounts of ammonia were formed, in addition to the reaction products seen without water present in the system. NO was found to photodesorb from graphite upon illumination with 355 nm light by a substrate-mediated mechanism. When silver clusters were added to the surface we found a clear dependence of the photoyield on the size and shape of the clusters.