Role of Cu Oxide and Cu Adatoms in the Reactivity of CO on Cu(110).

We investigate the interaction of CO with metallic and oxidized Cu(110) surfaces using a combination of near-ambient pressure scanning tunneling microscopy (NAP-STM) and theoretical calculations. While the Cu(110) and full CuO films are inert, the interface between bare Cu(110) and the CuO film is observed to react instantly with CO at a 10 mbar pressure. The reaction is observed to proceed from the interfacial sites of CuO/Cu(110). During reaction with CO, the CuO/Cu(110) interface releases Cu adatoms which combine with CO to produce a variety of added Cu-CO structures, whose stability depends on the gas pressure of CO. A main implication for the reactivity of Cu(110) is that Cu adatoms and highly undercoordinated CuO segments are created on the Cu(110) surface through the interaction with CO, which may act as reaction-induced active sites. In the case of CO hydrogenation to methanol, our theoretical assessment of such sites indicates that their presence may significantly promote CHOH formation. Our study thus implies that the CuO/Cu(110) interfacial system is highly dynamic in the presence of CO, and it suggests a possible strong importance of reaction-induced Cu and CuO sites for the surface chemistry of Cu(110) in CO-related catalysis.