While improved catalytic properties of many surfaces covered by two-dimensional materials have been demonstrated, a detailed in situ picture of gas delivery, undercover reaction, and product removal from the confined space is lacking. Here, we demonstrate how a combination of gas pulses with varying compositions and time-resolved ambient pressure photoelectron spectroscopy can be used to obtain such knowledge. This approach allows us to sequentially form and remove undercover reaction products, in contrast to previous work, where co-dosing of reactant gases was used. In more detail, we study CO and H₂ oxidation below oxygen-intercalated graphene flakes partially covering an Ir(111) surface. We show that hydrogen rapidly mixes into a p(2 × 1)-O structure below the graphene flakes and converts it into a dense OH–H₂O phase. In contrast, CO exposure only leads to oxygen removal from the confined space and little CO intercalation. Finally, our study shows that H₂ mixed into CO pulses can be used as a promoter to change the undercover chemistry. Their combined exposure leads to the formation of OH–H₂O below the flakes, which, in turn, unbinds the flakes for enough time for CO to intercalate, resulting in a CO structure stable only in coexistence with the OH–H₂O phase. Altogether, our study proves that promoter chemistry in the form of adding trace gases to the gas feed is essential to consider for undercover reactions.

中文翻译：

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遵循 APXPS 的卧底催化动力学和氢作为插层促进剂的作用

虽然已经证明了二维材料覆盖的许多表面的催化性能得到了改善，但缺乏气体输送、卧底反应和从密闭空间中去除产品的详细原位图片。在这里，我们展示了如何将具有不同成分的气体脉冲和时间分辨环境压力光电子能谱相结合来获得这些知识。与以前的工作相比，这种方法使我们能够顺序形成和去除隐藏的反应产物，其中使用了反应气体的共同给药。更详细地，我们研究了部分覆盖 Ir(111) 表面的氧插层石墨烯薄片下方的CO 和 H _2氧化。我们证明氢气会迅速混合成p石墨烯薄片下方的 (2 × 1)-O 结构将其转化为致密的 OH-H ₂ O 相。相比之下，CO 暴露只会导致从密闭空间中去除氧气，并且几乎没有 CO 嵌入。最后，我们的研究表明，混合到 CO 脉冲中的 H ₂可以作为促进剂来改变秘密化学。它们的联合暴露导致在薄片下方形成 OH-H ₂ O，这反过来又使薄片解开有足够的时间让 CO 嵌入，从而形成仅在与 OH-H ₂ O 相共存时才稳定的 CO 结构. 总之，我们的研究证明，在气体进料中添加痕量气体形式的促进剂化学对于秘密反应至关重要。