The low‐temperature water‐gas shift reaction (WGSR, CO+H₂O ⇔ H₂+CO₂) is considered a very promising reaction ‐candidate for fuel cells‐ despite an efficient and robust catalyst is still desirable. One of the more prominent catalysts for this reaction is based on single Pt atoms (Pt₁) on different supports, which are supposed to manifold the reaction by the accepted mechanism for the general WGSR, i. e. by addition of one H₂O molecule to CO, with generation of CO₂ and H₂. Here we show, experimentally, that not one but two H₂O molecules are added to CO on the Pt₁ catalyst, as assessed by a combination of reactivity experiments with soluble Pt catalysts, kinetic and spectroscopic measurements, and finally by in‐operando single crystal X‐ray diffraction on a Pt₁‐MOF, to visualize the formation of the hemiacetal intermediate on the solid catalytic site. These results confirm our previous DFT predictions and provide a paradigmatic shift in the assumed mechanism of the WGSR, which may open the debate if two H₂O molecules are recurrently added during the WGSR, not only for Pt₁ catalysts but also for other metal catalysts.

中文翻译：

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低温水煤气变换反应过程中Pt1-MOF上双水分子加成的晶体学可视化

低温水煤气变换反应（WGSR，CO + H ₂ ö⇔ħ ₂ + CO ₂）被认为是用于燃料细胞-一个非常有前途的反应-candidate尽管高效和稳健的催化剂仍然是需要的。用于该反应的最突出的催化剂之一是基于在不同载体上的单个Pt原子（Pt ₁），该载体应通过通用WGSR的公认机理（即，反应机理）来进行反应。e。通过向CO中添加一个H ₂ O分子，产生CO ₂和H ₂。在这里，我们通过实验表明，Pt ₁上的CO中没有添加一个，而是添加了两个H ₂ O分子催化剂，通过结合可溶性Pt催化剂的反应性实验，动力学和光谱测量，最后通过在Pt ₁ -MOF上进行操作中单晶X射线衍射进行评估，以可视化固体上半缩醛中间体的形成催化部位。这些结果证实了我们先前的DFT预测，并为WGSR的假定机理提供了范式转变，这可能引发争论，即在WGSR期间是否反复添加两个H ₂ O分子，不仅用于Pt ₁催化剂，还用于其他金属催化剂。