Abb Marcel J S, Weber Tim, Glatthaar Lorena, Over Herbert
Physikalisch-Chemisches Institut , Justus Liebig University , Heinrich-Buff-Ring 17 , 35392 Giessen , Germany.
Zentrum für Materialforschung , Justus Liebig University , Heinrich-Buff-Ring 16 , 35392 Giessen , Germany.
Langmuir. 2019 Jun 18;35(24):7720-7726. doi: 10.1021/acs.langmuir.9b00667. Epub 2019 Jun 5.
The growth of a flat, covering, and single-crystalline IrO(110) film with controlled film thickness on a single-crystalline TiO(110) substrate is reported. The preparation starts with a deposition of metallic Ir at room temperature followed by a post-oxidation step performed in an oxygen atmosphere of 10 mbar at 700 K. On this surface, additional Ir can be deposited at 700 K in an oxygen atmosphere of 10 mbar to produce a IrO(110) layer with variable thicknesses. To improve the crystallinity of the resulting IrO(110) layer, the final film was post-oxidized in 10 mbar of O at 700 K for 5 min. The surface-sensitive techniques of scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and low-energy electron diffraction (LEED) are employed to characterize the morphology, crystallinity, and electronic structure of the prepared ultrathin IrO(110) films and how these films decompose upon annealing under ultrahigh vacuum (UHV) conditions. STM provides evidence that the IrO(110) films start already to reduce at 465 K under UHV conditions. Upon annealing to 605 K under UHV the reduction of IrO intensifies (XPS), but the oxide film can readily be restored by re-oxidation in 10 mbar of O at 700 K. Thermal decomposition at 725 K leads, however, to severe reduction of the IrO(110) layer (XPS, STM) that cannot be restored by a subsequent re-oxidation step. The utility of the IrO(110)-TiO(110) system as model electrodes is exemplified with the electrochemical oxygen evolution reaction in an acidic environment.
报道了在单晶TiO(110)衬底上生长具有可控膜厚的平整、覆盖型单晶IrO(110)薄膜。制备过程始于室温下沉积金属Ir，随后在700 K、10 mbar的氧气气氛中进行后氧化步骤。在该表面上，可以在700 K、10 mbar的氧气气氛中额外沉积Ir，以制备具有可变厚度的IrO(110)层。为了提高所得IrO(110)层的结晶度，最终的薄膜在700 K、10 mbar的O₂中进行后氧化5分钟。采用扫描隧道显微镜（STM）、X射线光电子能谱（XPS）和低能电子衍射（LEED）等表面敏感技术来表征制备的超薄IrO(110)薄膜的形貌、结晶度和电子结构，以及这些薄膜在超高真空（UHV）条件下退火时如何分解。STM提供的证据表明，在UHV条件下，IrO(110)薄膜在465 K时就开始还原。在UHV条件下退火至605 K时，IrO的还原加剧（XPS），但通过在700 K、10 mbar的O₂中重新氧化，氧化膜可以很容易地恢复。然而，在725 K下的热分解会导致IrO(110)层严重还原（XPS、STM），后续的重新氧化步骤无法恢复。IrO(110)-TiO(110)系统作为模型电极在酸性环境中的电化学析氧反应中得到了应用。
