Role of Cu Oxide and Cu Adatoms in the Reactivity of CO₂ on Cu(110)

We investigate the interaction of CO₂ 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 CO₂ at a 10 mbar pressure. The reaction is observed to proceed from the interfacial sites of CuO/Cu(110). During reaction with CO₂, the CuO/Cu(110) interface releases Cu adatoms which combine with CO₃ to produce a variety of added Cu-CO₃ structures, whose stability depends on the gas pressure of CO₂. 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 CO₂, which may act as reaction-induced active sites. In the case of CO₂ hydrogenation to methanol, our theoretical assessment of such sites indicates that their presence may significantly promote CH₃OH formation. Our study thus implies that the CuO/Cu(110) interfacial system is highly dynamic in the presence of CO₂, and it suggests a possible strong importance of reaction-induced Cu and CuO sites for the surface chemistry of Cu(110) in CO₂-related catalysis.