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Water Oxidizing Diruthenium Electrocatalysts Immobilized on Carbon Nanotubes: Effects of the Number and Positioning of Pyrene Anchors
ACS Catalysis ( IF 12.9 ) Pub Date : 2020-08-24 , DOI: 10.1021/acscatal.0c01577
Sheida Rajabi 1 , Fatemeh Ebrahimi 2 , Gaurav Lole 2 , Jann Odrobina 1 , Sebastian Dechert 1 , Christian Jooss 2, 3 , Franc Meyer 1, 3
Affiliation  

The synthesis of efficient molecular water oxidation catalysts (WOCs) and their stable anchoring on suitable electron acceptor supports are crucial, yet challenging, steps for the development of artificial photosynthesis schemes. Here, a highly active diruthenium complex based on the bis(bipyridyl)pyrazolate (bbp) ligand scaffold is anchored on electronically conducting multiwall carbon nanotubes (MWCNTs) using a pyrene group attached to either the pyrazolate backbone (2) or to multiple axial ligand positions (1). High-resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS) show the presence of >75% sp2 hybridization of the MWCNTs and an increase of spectral weight of π–π* transitions upon immobilization of the pyrene-modified ligand or diruthenium complex, supporting pyrene anchoring via π–π interactions. Upon electrochemical oxidation the pyrene groups confined to the MWCNT-modified electrodes are rapidly converted to redox-active surface-bound quinone species. The water oxidation performance of the hybrid systems is studied by cyclic voltammetry and rotating ring disk electrode (RRDE) experiments under acidic aqueous condition (triflic acid, pH 1). Whereas the complex anchored at the backbone position shows higher initial catalytic activity, the complex anchored via four axial ligand positions features a higher stability. X-ray photoemission (XPS) data before and after electrochemical measurements reveal that the chemical structure of the immobilized complex remains intact under catalytic conditions. The results suggest that anchoring of Ru2 complexes by differently located pyrene groups on MWCNTs offers good performance for electron transfer, however, a single pyrene group at the pyrazolate backbone does not provide sufficiently strong surface attachment. The distinct experimental results for MWCNT hybrids with anchored 1 and 2 are further discussed in terms of the preferred attachment position at the pyrazolate-based Ru2 scaffold and the orientation of the catalyst’s active site with respect to the supporting surface.

中文翻译:

固定在碳纳米管上的水氧化二钌电催化剂:P锚的数量和位置的影响

高效分子水氧化催化剂(WOC)的合成及其在合适的电子受体载体上的稳定锚固是开发人工光合作用计划的关键但又具有挑战性的步骤。在这里,基于吡(酸酯双(bipyridyl)pyrazolate(bbp )配体骨架的高活性二钌络合物通过与吡唑酸酯骨架(2)或多个轴向配体相连的a基固定在导电的多壁碳纳米管(MWCNT)上位置(1)。高分辨率透射电子显微镜(HRTEM)和电子能量损失谱(EELS)显示存在> 75%sp 2im修饰的配体或二钌络合物固定后,MWCNT的杂化和π-π*跃迁的光谱重量增加,从而通过π-π相互作用支持了pyr的锚定。电化学氧化后,限制在MWCNT修饰电极上的pyr基迅速转变为氧化还原活性的表面结合醌类。通过循环伏安法和旋转环盘电极(RRDE)在酸性水溶液(三氟甲磺酸,pH 1)下的实验研究了混合系统的水氧化性能。锚固在骨架位置的复合物显示出较高的初始催化活性,而锚固在四个轴向配体位置的复合物具有较高的稳定性。电化学测量前后的X射线光发射(XPS)数据表明,在催化条件下,固定化配合物的化学结构保持完整。结果表明,Ru2络合物被MWCNT上不同位置的pyr基团锚固提供了良好的电子转移性能,但是,吡唑酸酯骨架上的单个pyr基团不能提供足够强的表面附着力。MWCNT与锚定杂种的独特实验结果关于吡唑基Ru 2支架上的优选附接位置以及催化剂的活性部位相对于支撑表面的取向,进一步讨论图1和图2
更新日期:2020-09-20
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