Assessing Optical and Electrical Properties of Highly Active IrOx Catalysts for the Electrochemical Oxygen Evolution Reaction via Spectroscopic Ellipsometry,ACS Catalysis

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Assessing Optical and Electrical Properties of Highly Active IrOx Catalysts for the Electrochemical Oxygen Evolution Reaction via Spectroscopic Ellipsometry
ACS Catalysis ( IF 11.3 ) Pub Date : 2020-11-20 , DOI: 10.1021/acscatal.0c03800
René Sachse _{1,

2} , Mika Pflüger ₃ , Juan-Jesús Velasco-Vélez _{4,

5} , Mario Sahre ₁ , Jörg Radnik ₁ , Michael Bernicke ₂ , Denis Bernsmeier ₂ , Vasile-Dan Hodoroaba ₁ , Michael Krumrey ₃ , Peter Strasser ₆ , Ralph Kraehnert ₂ , Andreas Hertwig ₁

Affiliation

Efficient water electrolysis requires highly active electrodes. The activity of corresponding catalytic coatings strongly depends on material properties such as film thickness, crystallinity, electrical conductivity, and chemical surface speciation. Measuring these properties with high accuracy in vacuum-free and non-destructive methods facilitates the elucidation of structure–activity relationships in realistic environments. Here, we report a novel approach to analyze the optical and electrical properties of highly active oxygen evolution reaction (OER) catalysts via spectroscopic ellipsometry (SE). Using a series of differently calcined, mesoporous, templated iridium oxide films as an example, we assess the film thickness, porosity, electrical resistivity, electron concentration, electron mobility, and interband and intraband transition energies by modeling of the optical spectra. Independently performed analyses using scanning electron microscopy, energy-dispersive X-ray spectroscopy, ellipsometric porosimetry, X-ray reflectometry, and absorption spectroscopy indicate a high accuracy of the deduced material properties. A comparison of the derived analytical data from SE, resonant photoemission spectroscopy, X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy with activity measurements of the OER suggests that the intrinsic activity of iridium oxides scales with a shift of the Ir 5d t_2g sub-level and an increase of p–d interband transition energies caused by a transition of μ₁-OH to μ₃-O species.

中文翻译：

通过光谱椭圆偏光法评估用于电化学放氧反应的高活性IrO _x催化剂的光电性能

有效的水电解需要高活性的电极。相应催化涂层的活性在很大程度上取决于材料性能，例如膜厚度，结晶度，电导率和化学表面形态。在无真空和非破坏性方法中高精度测量这些特性有助于阐明现实环境中的结构-活性关系。在这里，我们报告了一种新颖的方法，用于通过光谱椭偏仪（SE）分析高活性氧发生反应（OER）催化剂的光学和电学性质。以一系列不同煅烧的介孔模板氧化铱薄膜为例，我们评估了薄膜的厚度，孔隙率，电阻率，电子浓度，电子迁移率，通过对光谱进行建模，获得带间和带内跃迁能量。使用扫描电子显微镜，能量色散X射线光谱法，椭偏孔隙率法，X射线反射法和吸收光谱法进行的独立分析表明，推断出的材料特性具有很高的准确性。将SE，共振光发射光谱，X射线吸收光谱和X射线光电子能谱与OER活性测量得到的分析数据进行比较，结果表明，铱氧化物的固有活性随Ir 5d t的变化而变化。吸收光谱和吸收光谱表明推导的材料性能的高精度。将SE，共振光发射光谱，X射线吸收光谱和X射线光电子能谱与OER活性测量得到的分析数据进行比较，结果表明，铱氧化物的固有活性随Ir 5d t的变化而变化。吸收光谱和吸收光谱表明推导的材料性能的高精度。将SE，共振光发射光谱，X射线吸收光谱和X射线光电子能谱与OER活性测量得到的分析数据进行比较，结果表明，铱氧化物的固有活性随Ir 5d t的变化而变化。_2克子水平和增加P-d所引起的μ的过渡带间跃迁能量的₁ -OH到μ _3个-O物种。

更新日期：2020-12-04

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