The formation of supported metal/metal oxide single-atom catalysts (SAC), as well as their structural evolution during catalytic reactions have attracted much research interest in the fields of both inorganic chemistry and catalysis recently. In this work, we report the synthesis of iron (ca. 10 at%) oxide catalysts with the doping of a small amount (0.5–0.6 at%) of ruthenium oxide, which have been deposited onto the surface of ceria nanorods by an optimized deposition–precipitation (DP) route. Multiple characterization studies including X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and nitrogen adsorption/desorption confirmed the identical structural and textural properties of the ceria support after the DP step. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) combined with electron energy loss spectroscopy (EELS) showed the formation of subnanometer iron species in the fresh samples. Furthermore, the X-ray absorption fine structure (XAFS) technique with the help of related data analysis verified the generation of noncrystalline iron oxide clusters predominantly composed of Fe³⁺ ions. Here, the addition of a secondary metal (ruthenium) greatly promoted the dispersion of Fe over the ceria nanorods. After the catalytic reaction of Fischer–Tropsch synthesis (FTS), the transformation from subnanometer iron oxide species to ionic Fe^δ+ single atoms has been revealed and confirmed by the corresponding profile fits on the extended X-ray absorption fine structure (EXAFS) spectra. In contrast to the normal coarsening process, the FTS conditions (up to 300 °C, 2 MPa, CO/H₂ = 1/1) did drive the creation of such iron single atoms solely coordinated by oxygen ions.

中文翻译：

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费-托合成反应中二氧化铈负载的铁-钌氧化物催化剂的合成及其从亚纳米簇到单原子的结构转变

负载金属/金属氧化物单原子催化剂（SAC）的形成及其在催化反应过程中的结构演变最近在无机化学和催化领域引起了许多研究兴趣。在这项工作中，我们报告了铁的合成（约掺杂了少量（0.5–0.6 at％）氧化钌的10％氧化物氧化物催化剂，这些氧化物已通过优化的沉积-沉淀（DP）途径沉积在二氧化铈纳米棒的表面上。包括X射线衍射（XRD），高分辨率透射电子显微镜（HRTEM）和氮吸附/解吸在内的多项表征研究证实了DP步骤之后二氧化铈载体具有相同的结构和织构性质。像差校正的高角度环形暗场扫描透射电子显微镜（HAADF-STEM）与电子能量损失谱（EELS）的结合显示了新鲜样品中亚纳米铁的形成。此外，³⁺离子。在此，添加辅助金属（钌）极大地促进了Fe在二氧化铈纳米棒上的分散。费-托合成（FTS）的催化反应，从氧化亚纳米铁物种离子的Fe改造后^{δ +}单个原子已被发现并证实通过在扩展X射线吸收精细结构的相应轮廓配合（EXAFS）光谱。与正常的粗化过程相反，FTS条件（高达300°C，2 MPa，CO / H ₂ = 1/1）确实推动了仅由氧离子配位的此类铁单原子的产生。