Atomic layer deposition is a rising technique for catalyst synthesis and modification. Typically, the focus of ALD in catalysis is on supported metal nanoparticles. Here, the authors give mechanistic insights into the ALD of oxides on redox active catalysts by a combination of in situ analytics, such as XPS, DRIFTS and gravimetric measurements. Phosphorus oxide and aluminum oxide were deposited on divanadium pentoxide powder in a fixed bed reactor. In contrast to the generally accepted concepts, the first half cycle does not proceed over surface hydroxyl groups but involves redox chemistry between the precursor and the vanadium atoms, as shown by ³¹P-SSNMR and XPS. For PO_x deposition, a temperature step from 150 °C in the first half cycle to 450 °C in the second half cycle is needed to obtain linear mass gain per cycle as the remaining ligands are combusted and reduced vanadium atoms are reoxidized. Homogeneous deposition was confirmed by STEM-EDX and XRD showing no additional phases, despite performing up to 10 ALD cycles. Even the well-known process of alumina ALD confirms the involvement of reduction–oxidation reactions between the ALD precursor and the substrate V₂O₅. However, redox chemistry can be suppressed for alumina ALD at low temperatures of 50 °C. Therefore, this study shows that ALD on oxidation catalysts is complex and thus the developed ALD processes are unusual compared to ALD on typical supports, such as SiO₂ or Al₂O₃.

中文翻译：

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氧化催化剂上原子层沉积的机理研究-AlOx和POx沉积。

原子层沉积是用于催化剂合成和改性的新兴技术。通常，ALD在催化中的重点是负载的金属纳米颗粒。在这里，作者结合现场分析（例如XPS，DRIFTS和重量测量），对氧化还原活性催化剂上的氧化物的ALD进行了机械分析。在固定床反应器中，将氧化磷和氧化铝沉积在五氧化二钒粉末上。与通常接受的概念相反，前半周期不是在表面羟基上进行，而是涉及前体和钒原子之间的氧化还原化学反应，如³¹ P-SSNMR和XPS所示。对于PO _x在沉积过程中，需要进行从上半个周期的150°C到下半个周期的450°C的温度阶跃，以便随着剩余配体的燃烧和还原的钒原子的再氧化获得每个周期的线性质量增加。尽管执行了多达10个ALD循环，但STEM-EDX和XRD证实均相沉积没有显示其他相。甚至众所周知的氧化铝ALD工艺也证实了ALD前驱体与基材V ₂ O ₅之间存在还原-氧化反应。但是，在50°C的低温下可以抑制氧化铝ALD的氧化还原化学作用。因此，这项研究表明，氧化催化剂上的ALD是复杂的，因此与常规载体（如SiO _2）上的ALD相比，已开发的ALD工艺是不寻常的或Al ₂ O ₃。