Investigation of adsorption and coadsorption of O2 and CO on Rh by O2+ field ion and Li+ field desorption microscopies

A recently developed new method, the lithium field desorption microscopy as well as the O2+ field ion microscopy were applied for studying the clean, the carbon monoxide- and the oxygen-covered surfaces of [100]- and [111]-oriented Rh tips. The catalytic CO-oxidation reaction on the Rh surface was studied in situ using Li+ and O2+ field ion modes of imaging. The peculiarities of imaging of different surfaces in the Li FDM are discussed in terms of field-stimulated surface diffusion of Li, of the localization of the Li field desorption process and the lateral interaction between Li adatoms. A roughening of the oxygen-covered Rh surface is observed and explained in terms of an oxygen-caused reconstruction of the Rh surface. A substantial influence of the electron density modification near the surface, caused by the presence of Li, on the CO-oxidation reaction on Rh is detected. The promoting role of the enhanced electron density in the catalytic oxidation reaction is discussed on the basis of present experimental data and known alkali-gas coadsorption properties.