High-pressure NO-induced mixed phase on Rh(111): Chemically driven replacement

The interaction between nitric oxide (NO) and Rh(111) surface has been investigated by a combination of near-ambient-pressure X-ray photoelectron spectroscopy, low energy electron diffraction, and density functional theory calculations. Under low-temperature and ultrahigh vacuum conditions, our experimental and computational results are consistent with the previous reports for NO adsorption phases on Rh(111). While at room temperature and upon exposure to gaseous NO of 100 mTorr, NO molecules partially dissociate followed by chemical removal of atomic nitrogen by NO from the surface, and the remaining atomic oxygen and NO form a NO/O mixed phase. Interestingly, this mixed phase is stable even after NO evacuation and shows a well-ordered (2 × 2) periodicity. These observations provide a new insight into the NO/Rh(111) system under near-ambient-pressure condition.