ONE-DIMENSIONAL REACTIVITY IN CATALYSIS STUDIED WITH THE SCANNING TUNNELING MICROSCOPE

THE scanning tunnelling microscope (STM) has yielded great insight int o the structure of surfaces and into the dynamics of surface reconstru ction and adsorption1. We show here that it can also provide direct in formation about the microscopic mechanisms of catalytic reactions on s urfaces. We have studied the oxidation of carbon monoxide on an oxygen -precovered rhodium (110) surface, a process related to the catalytic removal of CO in exhaust gases2,3. The STM images show that the reacti vity is strongly influenced by the oxygen-induced reconstructions of t he surface. The reaction is initiated at high-energy adsorption sites, mainly at steps and domain boundaries of the adsorbed oxygen layer. T he CO strips away one-dimensional islands of oxygen atoms on the recon structed surface, proceeding in the [011] direction. More generally, t hese results show how the STM can provide insights into the microkinet ics of surface reactions.