The mechanism of a low-temperature water-gas shift reaction (LT-WGSR) over supported gold catalysts has long been disputed, with the two prevailing ones being redox and associative mechanisms, due to the rather limited direct and reliable evidence for the actual reaction route. Herein, a typical supported gold-based catalyst (Au@TiO_2−x/ZnO) was obtained via a structural topotactic transformation from hydrotalcite precursors, exhibiting an extremely high catalytic performance towards LT-WGSR. A series of experimental measurements involving in situ/operando DRIFTS, in situ Pulse-MASS and in situ/operando EXAFS as well as density functional theory (DFT) calculations were carried out to monitor the dynamic evolution of active sites, detect reaction intermediates and identify the reaction route. A new redox reaction route derived from the interfacial synergistic catalysis was verified: one H₂O molecule undergoes dissociation at an Au^δ−–O_v–Ti³⁺ (O_v: oxygen vacancy) interfacial active site, accompanied with the production of one H₂ molecule and the oxidation of the interfacial structure to Au⁰–O_r–Ti⁴⁺ (O_r: the interfacial reactive oxygen species). Subsequently, one chemisorbed CO molecule captures O_r to produce CO₂ with the recovery of Au^δ−–O_v–Ti³⁺. The present understanding and identification of the reaction mechanism of LT-WGSR would offer inspiration for further material exploration and catalyst design in gold-based heterogeneous catalysis.

中文翻译：

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Au @ TiO2-x / ZnO催化剂对低温水煤气变换反应的催化机理

负载型金催化剂上的低温水煤气变换反应（LT-WGSR）的机理长期以来一直存在争议，主要的两种是氧化还原和缔合机理，因为对于实际反应而言，直接和可靠的证据相当有限路线。在此，通过水滑石前体的结构电位转变获得了典型的负载型金基催化剂（Au @ TiO _{2- x} / ZnO），表现出对LT-WGSR的极高的催化性能。一系列实验测量，包括原位/手术DRIFTS，原位Pulse-MASS和原位/手术进行了EXAFS以及密度泛函理论（DFT）的计算，以监测活性位点的动态演变，检测反应中间体并确定反应路线。验证了一种由界面协同催化作用产生的新的氧化还原反应途径：一个H ₂ O分子在^Auδ-- O _v -Ti ³⁺（O _v：氧空位）界面活性部位发生离解，并伴随一个H ₂分子和界面结构被氧化为Au ⁰ –O _r –Ti ⁴⁺（O _r：界面活性氧种类）。随后，一个化学吸附的CO分子捕获了O _r并产生了CO ₂，并回收了^Auδ-- O _v -Ti ³⁺。目前对LT-WGSR反应机理的理解和鉴定将为进一步的金基多相催化材料探索和催化剂设计提供启示。