Atomic-Scale Dynamic Interaction of H2O Molecules with Cu Surface

Atomic-scale interaction of water vapor with metal surfaces beyond surface adsorption under technologically relevant conditions remains mostly unexplored. Using aberration-corrected environmental transmission electron microscopy, we reveal the dynamic surface activation of Cu by ${\mathrm{H}}_{2}\mathrm{O}$ at elevated temperature and pressure. We find a structural transition from flat to corrugated surface for the Cu(011) under low water-vapor pressure. Increasing the water-vapor pressure leads to the surface reaction of Cu with dissociated ${\mathrm{H}}_{2}\mathrm{O}$, resulting in the formation of a metastable ``bilayer'' $\mathrm{Cu}─\mathrm{O}─\mathrm{H}$ phase. Corroborated by density functional theory and ab initio molecular dynamics calculations, the cooperative O and OH interaction with Cu is responsible for the formation and subsurface propagation of this phase.