原位检测氧化态 ≥ IV 的钴-铁羟基氧化物在析氧反应中重建,Advanced Energy Materials

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原位检测氧化态 ≥ IV 的钴-铁羟基氧化物在析氧反应中重建
Advanced Energy Materials ( IF 24.4 ) Pub Date : 2023-02-02 , DOI: 10.1002/aenm.202203886
Lukas Reith ₁ , Jan Niklas Hausmann ₁ , Stefan Mebs ₂ , Indranil Mondal ₁ , Holger Dau ₂ , Matthias Driess ₁ , Prashanth W. Menezes _{1,

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Affiliation

钴铁羟基氧化物 (CoFeOOH _x ) 是析氧反应 (OER) 中最活跃的催化剂之一。然而，它们的氧化还原行为及其活性位点的电子和化学结构仍然不明确。为了更清楚地阐明这一点，可以实现将四种具有不同 Co:Fe 比例的螺旋钴铁硼磷酸盐完全快速地重构为无序的钴铁氢氧化物，这些氢氧化钴是电解质可渗透的，因此大多数过渡金属位点都可能参与开放教育资源。为了跟踪氧化还原行为并识别活性结构，应用了准原位 X 射线吸收光谱。高氧化态铁 ≥ IV (Fe ⁴⁺) 及其大量的氧化还原行为，平均氧化态约为 2.8 至 3.2 以上。此外，在 OER 期间观察到与 Fe ³⁺ OOH 参考相比，Fe-O 键长收缩了 6%，并且确定了[MO _{6 ] 八面体的强烈变形。}据推测，这种键收缩是由氧自由基的存在引起的，并且二-μ-氧自由基桥接的钴-铁中心是活性位点。预计详细的电子和结构描述可以大大有助于讨论双金属含铁 OER 催化剂中活性位点的性质。

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In Situ Detection of Iron in Oxidation States ≥ IV in Cobalt-Iron Oxyhydroxide Reconstructed during Oxygen Evolution Reaction

Cobalt-iron oxyhydroxides (CoFeOOH_x) are among the most active catalysts for the oxygen evolution reaction (OER). However, their redox behavior and the electronic and chemical structure of their active sites are still ambiguous. To shed more light on this, the complete and rapid reconstruction of four helical cobalt-iron borophosphates with different Co:Fe ratios into disordered cobalt-iron oxyhydroxides can be achieved, which are electrolyte-penetrable and thus most transition metal sites can potentially participate in the OER. To track the redox behavior and to identify the active structure, quasi in situ X-ray absorption spectroscopy is applied. Iron in high oxidation states ≥ IV (Fe⁴⁺) and its substantial redox behavior with an average oxidation state of around 2.8 to above 3.2 is detected. Furthermore, a 6% contraction of the Fe-O bond length compared to Fe³⁺OOH references is observed during OER and a strong distortion of the [MO₆] octahedra is identified. It is hypothesized that this bond contraction is caused by the presence of oxyl radicals and that di-µ-oxyl radical bridged cobalt-iron centers are the active sites. It is anticipated that the detailed electronic and structural description can substantially contribute to the debate on the nature of the active site in bimetallic iron-containing OER catalysts.

更新日期：2023-02-02

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