Cyclic and repeatable CO/H formation under periodic CO ↔ HO feeds, that is unsteady-state water–gas shift reaction (uss-WGS), was found to be catalyzed by a gold nanoparticles-loaded CeO (Au/CeO) catalyst. Kinetics of the CO-reduction of Ce to Ce and Ce reoxidation by HO in combination with transient CO/H formation over Au/CeO were studied by ultraviolet–visible (UV–vis) and infrared (IR) spectroscopies at 175 °C. The Ce–OH species were reduced by CO to give Ce-□-Ce (□: oxygen vacancy) and gas phase products (H, CO). The Ce-□-Ce species were oxidized by HO to give H and Ce–OH species. The reduction and reoxidation rates of Ce/Ce redox couple were close to the rates of transient CO/H formation. The X-ray absorption spectroscopy results showed that the oxidation states of Au remained unchanged during the redox reactions. These results indicate that the uss-WGS is primary driven by the Ce/Ce redox couple. Combined with the observation of adsorbed carboxylate intermediates as a precursor of H and CO, associative redox mechanism is proposed as the main pathway for the unsteady-state WGS reaction on Au/CeO at 175 °C.

中文翻译：

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Au/CeO2 催化剂上周期性非稳态水煤气变换反应缔合氧化还原机制的原位/操作光谱证据

在周期性 CO ↔ H2O 进料下循环且可重复地形成 CO/H，即非稳态水煤气变换反应 (uss-WGS)，被发现是由负载金纳米颗粒的 CeO (Au/CeO) 催化剂催化的。通过紫外可见 (UV-vis) 和红外 (IR) 光谱在 175 °C 下研究了 Ce CO 还原为 Ce 和 Ce 再氧化以及 Au/CeO 上瞬时 CO/H 形成的动力学。 Ce-OH物种被CO还原，得到Ce-□-Ce（□：氧空位）和气相产物（H、CO）。 Ce-□-Ce 物质被 H2O 氧化，得到 H 和 Ce-OH 物质。 Ce/Ce氧化还原对的还原和再氧化速率接近瞬时CO/H形成速率。 X射线吸收光谱结果表明，Au的氧化态在氧化还原反应过程中保持不变。这些结果表明 uss-WGS 主要由 Ce/Ce 氧化还原对驱动。结合吸附的羧酸盐中间体作为 H 和 CO 前体的观察，提出缔合氧化还原机制是 Au/CeO 在 175 °C 下非稳态 WGS 反应的主要途径。