The oxygen adsorption and its catalytic reaction with hydrogen on Pt–Rh single crystals were studied at the nanoscale by Field Emission Microscopy (FEM) and Field Ion Microscopy (FIM) techniques at 700 K. Both FEM and FIM use samples prepared as sharp tips, apexes of which mimic a single nanoparticle of catalyst considering their similar size and morphology. Oxygen adsorption on Pt-17.4 at.%Rh samples leads to the formation of subsurface oxygen, which is manifested in the field emission (FE) patterns: for O₂ exposure of ~3 Langmuir (L), {113} planes appear bright in the emission pattern, while for higher oxygen doses, i.e. 84 L, the bright regions correspond to the high index planes between the {012} and {011} planes. Formation of subsurface oxygen is probably accompanied by a surface reconstruction of the nanocrystal. The subsurface oxygen can be effectively reacted off by subsequent exposure of the sample to hydrogen gas at 700 K. The hydrogenation reaction was observed as a sudden, eruptive change of the brightness seen on the FE pattern. This reaction resulted in the recovery of the initial field emission pattern characteristic of a clean tip, with {012} facets being the most visible. It was shown that the oxygen accumulation-reduction process is completely reversible. The obtained results indicate that the presence of subsurface species must be considered in the description of reactive processes on Pt–Rh catalysts.

在700 K下，通过场发射显微镜（FEM）和场离子显微镜（FIM）技术在纳米级研究了Pt–Rh单晶上的氧吸附及其与氢的催化反应。FEM和FIM均使用制备为尖锐尖端的样品，考虑到它们相似的大小和形态，其顶点模仿催化剂的单个纳米颗粒。氧气在Pt-17.4 at。％Rh样品上的吸附会导致地下氧气的形成，这在场发射（FE）模式中表现出来：对于O ₂〜3 Langmuir（L）的曝光，{113}平面在发射模式中显得很亮，而对于较高的氧气剂量，即84 L，亮区域对应于{012}和{011}平面之间的高折射率平面。地下氧的形成可能伴随着纳米晶体的表面重建。通过随后将样品暴露于700 K的氢气中，可以有效地释放出地下氧气。观察到氢化反应是在FE图案上看到的亮度突然爆发性变化。该反应导致了干净尖端的初始场发射图案特性的恢复，其中最明显的是{012}刻面。结果表明，氧积累-还原过程是完全可逆的。