Pentanuclear iron complex for water oxidation: spectroscopic analysis of reactive intermediates in solution and catalyst immobilization into the MOF-based photoanode.
Pentanuclear iron complex for water oxidation: spectroscopic analysis of reactive intermediates in solution and catalyst immobilization into the MOF-based photoanode.
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DOI：
10.1016/j.jcat.2023.115230
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发表时间：
2023-11
影响因子：
7.3
通讯作者：
Roman Ezhov;G. Bury;Olga Maximova;Elliot Daniel Grant;Mio Kondo;Shigeyuki Masaoka;Yulia Pushkar
中科院分区：
文献类型：
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作者：
Roman Ezhov;G. Bury;Olga Maximova;Elliot Daniel Grant;Mio Kondo;Shigeyuki Masaoka;Yulia Pushkar
光电化学水裂解可以生产绿色氢气用于工业用途和二氧化碳中性运输，确保从化石燃料过渡到绿色可再生能源。铁基电催化剂[FeII 4FeIII（μ-3-O）（μ-L）6]3+（LH = 3，5-双（2-吡啶基）吡唑）（1）于2016年发现，是基于地球丰富元素的最快分子水氧化催化剂（WOC）之一。然而，其水氧化反应（WOR）机制尚未完全阐明。本文用X射线能谱和电子顺磁共振（EPR）研究了（1）在水-乙腈溶液中促进的电化学WOR。我们观察到瞬态反应中间体在theinsituelectrochemical WOR，与协调球膨胀之前的催化电流的发病。在预催化电位（Ag/AgCl +1.1 Vvs.Ag/AgCl）下，观察到明显的g = 2.0 EPR信号，归属于Fe Ⅲ/Fe Ⅳ相互作用。在催化电位（V +1.6 Vvs.Ag/AgCl）下长时间电解导致（1）中Fe中心的进一步氧化，在此电解达到稳态时，通过XANES和EXAFS拟合，推测形成了高价FeV双键O和FeIV双键O催化中间体，在V +1.6 Vvs. Ag/AgCl处检测到一个短的Fe双键O键.（1）嵌入MIL-126 MOF中，形成（1）-MIL-126复合材料。后者在光电化学WOR中进行了测试，并证明了在酸性（pH = 2）水溶液中可见光照射时电催化电流的增加。所提出的光谱分析提供了进一步深入了解多核系统的催化途径，并应有助于随后开发基于地球丰富的金属的更具能源和成本效益的水裂解催化剂。（1）-MIL-126的光电催化活性证实了在固体载体内产生（1）的组装体并利用太阳辐射实现催化剂的工业应用的可能性。
Photoelectrochemical water splitting can produce green hydrogen for industrial use and CO2-neutral transportation, ensuring the transition from fossil fuels to green, renewable energy sources. The iron-based electrocatalyst [FeII4FeIII(μ-3-O)(μ-L)6]3+(LH = 3,5-bis(2-pyridyl)pyrazole)(1), discovered in 2016, is one of the fastest molecular water oxidation catalysts (WOC) based on earth-abundant elements. However, its water oxidation reaction (WOR) mechanism has not been yet fully elucidated. Here, we presentin situX-ray spectroscopy and electron paramagnetic resonance (EPR) analysis of electrochemical WOR promoted by(1)in water-acetonitrile solution. We observed transient reactive intermediates during thein situelectrochemical WOR, consistent with a coordination sphere expansion prior to the onset of catalytic current. At a pre-catalytic (∼+1.1 Vvs.Ag/AgCl) potential, the distinct g ∼ 2.0 EPR signal assigned to FeIII/FeIVinteraction was observed. Prolonged bulk electrolysis at catalytic (∼+1.6 Vvs.Ag/AgCl) potential leads to the further oxidation of Fe centers in(1).At the steady state achieved with such electrolysis, the formation of hypervalent FeVdouble bondO and FeIVdouble bondO catalytic intermediates was inferred with XANES and EXAFS fitting, detecting a short Fedouble bondO bond at ∼ 1.6 Å.(1)was embedded into MIL-126 MOF with the formation of a(1)-MIL-126 composite. The latter was tested in photoelectrochemical WOR and demonstrated an increase in electrocatalytic current upon visible light irradiation in acidic (pH = 2) water solution. The presented spectroscopic analysis gives further insight into the catalytic pathways of multinuclear systems and should help the subsequent development of more energy- and cost-effective water-splitting catalysts based on earth-abundant metals. Photoelectrocatalytic activity of(1)-MIL-126 confirms the possibility of creating an assembly of(1)inside a solid support and harnessing solar irradiation towards industrial applications of the catalyst.