Comini Nicolo, Diulus J Trey, Parkinson Gareth S, Osterwalder Jürg, Novotny Zbynek
Physik-Institut, Universität Zürich, Zürich CH-8057, Switzerland.
Swiss Light Source, Paul Scherrer Institut, Villigen-PSI CH-5232, Switzerland.
J Phys Chem C Nanomater Interfaces. 2023 Sep 14;127(38):19097-19106. doi: 10.1021/acs.jpcc.3c03097. eCollection 2023 Sep 28.
Stable single metal adatoms on oxide surfaces are of great interest for future applications in the field of catalysis. We studied iridium single atoms (Ir) supported on a FeO(001) single crystal, a model system previously only studied in ultra-high vacuum, to explore their behavior upon exposure to several gases in the millibar range (up to 20 mbar) utilizing ambient-pressure X-ray photoelectron spectroscopy. The Ir single adatoms appear stable upon exposure to a variety of common gases at room temperature, including oxygen (O), hydrogen (H), nitrogen (N), carbon monoxide (CO), argon (Ar), and water vapor. Changes in the Ir 4f binding energy suggest that Ir interacts not only with adsorbed and dissociated molecules but also with water/OH groups and adventitious carbon species deposited inevitably under these pressure conditions. At higher temperatures (473 K), iridium adatom encapsulation takes place in an oxidizing environment (a partial O pressure of 0.1 mbar). We attribute this phenomenon to magnetite growth caused by the enhanced diffusion of iron cations near the surface. These findings provide an initial understanding of the behavior of single atoms on metal oxides outside the UHV regime.
氧化物表面稳定的单金属原子对于催化领域的未来应用具有重大意义。我们研究了负载在FeO(001)单晶上的铱单原子（Ir），这是一个此前仅在超高真空条件下研究过的模型体系，利用常压X射线光电子能谱来探索它们在暴露于毫巴范围（高达20毫巴）的几种气体时的行为。在室温下，Ir单原子在暴露于各种常见气体时显得稳定，这些气体包括氧气（O）、氢气（H）、氮气（N）、一氧化碳（CO）、氩气（Ar）和水蒸气。Ir 4f结合能的变化表明，Ir不仅与吸附和解离的分子相互作用，还与在这些压力条件下不可避免沉积的水/OH基团和外来碳物种相互作用。在较高温度（473 K）下，铱单原子在氧化环境（0.1毫巴的O分压）中会发生包裹现象。我们将此现象归因于表面附近铁阳离子扩散增强导致的磁铁矿生长。这些发现为超高真空环境之外的金属氧化物上单原子的行为提供了初步认识。
