Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland.
Glas Trösch AG, Industriestrasse 29, 4922 Bützberg, Switzerland.
Sci Rep. 2017 Mar 22;7:43369. doi: 10.1038/srep43369.
Rare-earth (RE) oxide surfaces are of significant importance for catalysis and were recently reported to possess intrinsic hydrophobicity. The surface chemistry of these oxides in the low temperature regime, however, remains to a large extent unexplored. The reactions occurring at RE surfaces at room temperature (RT) in real air environment, in particular, in presence of polycyclic aromatic hydrocarbons (PAHs), were not addressed until now. Discovering these reactions would shed light onto intermediate steps occurring in automotive exhaust catalysts before reaching the final high operational temperature and full conversion of organics. Here we first address physical properties of the RE oxide, nitride and fluoride surfaces modified by exposure to ambient air and then we report a room temperature reaction between PAH and RE oxide surfaces, exemplified by tetracene (CH) on a GdO. Our study evidences a novel effect - oxidation of higher hydrocarbons at significantly lower temperatures (~300 K) than previously reported (>500 K). The evolution of the surface chemical composition of RE compounds in ambient air is investigated and correlated with the surface wetting. Our surprising results reveal the complex behavior of RE surfaces and motivate follow-up studies of reactions between PAH and catalytic surfaces at the single molecule level.
稀土（RE）氧化物表面对于催化具有重要意义，最近有报道称其具有固有疏水性。然而，这些氧化物在低温条件下的表面化学性质在很大程度上仍未得到探索。直到现在，人们才开始研究 RE 表面在室温（RT）下在实际空气环境中发生的反应，特别是在多环芳烃（PAHs）存在的情况下。发现这些反应将有助于揭示在达到最终高操作温度和有机物完全转化之前，汽车尾气催化剂中发生的中间步骤。在这里，我们首先研究了暴露于环境空气中的 RE 氧化物、氮化物和氟化物表面的物理性质，然后报告了 PAH 和 RE 氧化物表面之间在室温下的反应，以 GdO 上的四环（CH）为例。我们的研究证明了一种新的效应——在比以前报道的（>500 K）低得多的温度（~300 K）下氧化更高的碳氢化合物。研究了环境空气中 RE 化合物表面化学组成的演变，并将其与表面润湿性相关联。我们令人惊讶的结果揭示了 RE 表面的复杂行为，并激发了在单分子水平上研究 PAH 和催化表面之间反应的后续研究。
