Ruthenium-copper: a model bimetallic system for studies of surface chemistry and catalysis

Abstract

The combination of metallic elements ruthenium and copper is an intriguing one for studies of the surface chemistry and catalytic properties of bimetallic systems. Although the two metals are completely immiscible in the bulk, they form bimetallic entities in which copper is present on the surface of ruthenium. The initial conclusions about the nature of these entities were derived solely from measurements of chemisorption isotherms and reaction rates on ruthenium-copper catalysts. Later studies of the catalysts using physical probes such as X-ray photoelectron spectroscopy and extended X-ray absorption fine structure provided valuable confirmation of the early conclusions. Eventually, studies were initiated with specimens prepared by vapour deposition of copper on to the surfaces of ruthenium single crystals. These investigations have employed most of the sophisticated probes of modern surface science. As one can readily see from the literature, the ruthenium-copper system has attracted much attention in surface chemistry and catalysis. It has become an important model system for elucidating fundamental questions related to the performance of bimetallic catalysts. This review brings together the results of published work on typical ruthenium-copper catalysts and their single crystal counterparts.