Chakarova Kristina K, Mihaylov Mihail Y, Karapenchev Bayan S, Drenchev Nikola L, Ivanova Elena Z, Vayssilov Georgi N, Aleksandrov Hristiyan A, Hadjiivanov Konstantin I
Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria.
Faculty of Chemistry and Pharmacy, University of Sofia, 1126 Sofia, Bulgaria.
Molecules. 2025 Jul 24;30(15):3100. doi: 10.3390/molecules30153100.
Ceria is an important redox catalyst due to the facile Ce/Ce switching at its surface. Therefore, in situ determination of the oxidation state of surface cerium cations is of significant interest. Infrared spectroscopy of probe molecules such as CO holds great potential for this purpose. However, the ability of CO to reduce Ce cations is an important drawback as it alters the initial cerium speciation. Dinitrogen (N), due to its chemical inertness, presents an attractive alternative. We recently demonstrated that low-temperature N adsorption on stoichiometric ceria leads to the formation of complexes with Ce cations on the (110) and (100) planes (bands at 2257 and 2252 cm, respectively), while the (111) plane is inert. Here, we report results on the low-temperature N adsorption on reduced ceria nanoshapes (cubes, polyhedra, and rods). A main band at 2255 cm, with a weak shoulder at 2254 cm, was observed. We attributed these bands to N adsorbed on Ce sites located on edges and corners as well as on {100} facets. In conclusion, N adsorbs on the most acidic surface Ce sites and enables their distinction from Ce cations.
由于铈在其表面易于进行Ce⁴⁺/Ce³⁺转换，二氧化铈是一种重要的氧化还原催化剂。因此，原位测定表面铈阳离子的氧化态具有重大意义。诸如CO等探针分子的红外光谱在这方面具有很大潜力。然而，CO还原Ce阳离子的能力是一个重要缺点，因为它会改变初始铈的形态。由于氮气（N₂）具有化学惰性，它是一种有吸引力的替代物。我们最近证明，化学计量比的二氧化铈在低温下吸附N₂会导致在（110）和（100）平面上与Ce阳离子形成络合物（分别在2257和2252 cm⁻¹处出现谱带），而（111）平面是惰性的。在此，我们报告了还原态二氧化铈纳米形状（立方体、多面体和棒状体）在低温下吸附N₂的结果。观察到一个位于2255 cm⁻¹的主谱带，在2254 cm⁻¹处有一个弱肩峰。我们将这些谱带归因于吸附在位于边缘、角落以及{100}晶面上的Ce位点上的N₂。总之，N₂吸附在酸性最强的表面Ce位点上，并能够将它们与Ce阳离子区分开来。
