Homogeneous Electrochemical Water Oxidation at Neutral pH by Water-Soluble NiII Complexes Bearing Redox Non-innocent Tetraamido Macrocyclic Ligands.,ChemSusChem

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Homogeneous Electrochemical Water Oxidation at Neutral pH by Water-Soluble NiII Complexes Bearing Redox Non-innocent Tetraamido Macrocyclic Ligands.
ChemSusChem ( IF 7.5 ) Pub Date : 2020-03-31 , DOI: 10.1002/cssc.202000153
Husileng Lee ₁ , Xiujuan Wu ₁ , Licheng Sun _{1,

2,

3}

Affiliation

Water oxidation is the bottleneck reaction in artificial photosynthesis. Exploring highly active and stable molecular water oxidation catalysts (WOCs) is still a great challenge. In this study, a water‐soluble Ni^II complex bearing a redox non‐innocent tetraamido macrocyclic ligand (TAML) is found to be an efficient electrocatalyst for water oxidation in neutral potassium phosphate buffer. Controlled‐potential electrolysis experiments show that it can sustain at a steady current of approximately 0.2 mA cm⁻² for >7 h at 1.75 V versus normal hydrogen electrode (NHE) without the formation of NiO_x. Electrochemical and spectroelectrochemical tests show that the redox‐active ligand, as well as HPO₄²⁻ in the buffer, participate in the catalytic cycle. More importantly, catalytically active intermediate [Ni^III(TAML²⁻)−O^.] is formed via several proton‐coupled electron transfer processes and reacts with H₂O with the assistance of base to release molecular oxygen. Thus, the employment of redox non‐innocent ligands is a useful strategy for designing effective molecular WOCs.

中文翻译：

带有氧化还原非清纯四酰胺基大环配体的水溶性NiII络合物在中性pH下进行均相电化学水氧化。

水的氧化是人工光合作用的瓶颈反应。探索高活性和稳定的分子水氧化催化剂（WOC）仍然是一个巨大的挑战。在这项研究中，发现带有氧化还原非纯四酰胺基大环配体（TAML）的水溶性Ni ^II络合物是中性磷酸钾缓冲液中水氧化的有效电催化剂。受控电位电解实验表明，与正常的氢电极（NHE）相比，它在1.75 V的稳定电流下，在约0.2 mA cm ^-2的恒定电流下可维持> 7 h的时间，而不会形成NiO _x。电化学和光谱电化学测试表明，氧化还原活性配体以及HPO ₄^2-在缓冲液中，参与催化循环。更重要的是，具有催化活性的中间体[Ni ^III（TAML ^2-）-O ^。]是通过几个质子耦合的电子转移过程形成的，并在碱的帮助下与H ₂ O反应释放出分子氧。因此，采用氧化还原非纯配体是设计有效分子WOC的有用策略。

更新日期：2020-03-31

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