多频 EPR 揭示用于制氢的分子钴催化剂的电子结构,The Journal of Physical Chemistry C

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多频 EPR 揭示用于制氢的分子钴催化剂的电子结构
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2022-07-19 , DOI: 10.1021/acs.jpcc.2c02576
Jens Niklas ₁ , Lars Kohler ₁ , Andrea M. Potocny ₁ , Kristy L. Mardis ₂ , Karen L. Mulfort ₁ , Oleg G. Poluektov ₁

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改进析氢反应 (HER) 催化剂的设计需要详细了解催化剂的结构和环境。我们使用多频电子顺磁共振 (EPR) 光谱（X 波段、Q 波段和 D 波段）结合密度泛函理论 (DFT) 建模来阐明 H 的三种 Co(II) 分子催化剂的电子结构₂演化以确定电子结构参数与催化活性和稳定性的相关性。这里研究的 Co(II) 配位配合物代表两种类型的 H ₂-不断发展的分子催化剂：钴肟，由钴配位到两个乙二肟配体形成，以及钴聚（吡啶基）配合物，通常具有四个或五个吡啶基配体与单个 Co（II）离子配位。这些 Co(II) 配合物在多种溶剂中进行了研究，这些溶剂具有一系列极性和化学计量的钴离子潜在配体，以评估配体-钴相互作用的强度和性质。使用 EPR 光谱获得的磁共振参数作为参考数据，我们在 DFT 建模的帮助下重建了 Co(II) 配合物的电子结构。对于所有三种催化剂，我们发现 Co(II) A _z值与g _x之间存在线性相关性。值取决于轴向配体的强度。我们在电子结构和金属配位环境之间建立的相关性提供了对支撑所观察到的 HER 催化活性趋势的结构和电子因素的深入了解。

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Electronic Structure of Molecular Cobalt Catalysts for H2 Production Revealed by Multifrequency EPR

Improving the design of hydrogen evolution reaction (HER) catalysts requires a detailed understanding of the catalyst’s structure and environment. We have used multifrequency electron paramagnetic resonance (EPR) spectroscopy (X-band, Q-band, and D-band) in combination with density functional theory (DFT) modeling to elucidate the electronic structure of three Co(II) molecular catalysts for H₂ evolution to determine correlations of electronic structure parameters with catalytic activity and stability. The Co(II) coordination complexes investigated here are representative of two types of H₂-evolving molecular catalysts: cobaloximes, formed from cobalt coordination to two glyoxime ligands, and cobalt poly(pyridyl) complexes, which commonly have either four or five pyridyl ligands coordinating a single Co(II) ion. These Co(II) complexes were studied in a variety of solvents with a range of polarities and stoichiometric amounts of potential ligands to the cobalt ion to assess the strength and nature of ligand–cobalt interactions. Using magnetic resonance parameters obtained by EPR spectroscopy as reference data, we reconstructed the electronic structure of the Co(II) complexes with the help of DFT modeling. For all three catalysts, we uncovered a linear correlation between the Co(II) A_z value and the g_x value that is dependent on the strength of the axial ligands. The correlations that we have established between the electronic structure and metal coordination environment provide insight into the structural and electronic factors underpinning the observed trends in HER catalysis activity.

更新日期：2022-07-19

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