Immobilization of “Capping Arene” Cobalt(II) Complexes on Ordered Mesoporous Carbon for Electrocatalytic Water Oxidation
Immobilization of “Capping Arene” Cobalt(II) Complexes on Ordered Mesoporous Carbon for Electrocatalytic Water Oxidation
复制标题
DOI：
10.1021/acscatal.1c04617
复制
发表时间：
2021-12
期刊：
影响因子：
12.9
通讯作者：
Chang Liu;Ana M. Geer;Christopher Webber;C. Musgrave;Shunyan Gu;Grayson Johnson;D. Dickie;S. Chabbra
中科院分区：
文献类型：
--
作者：
Chang Liu;Ana M. Geer;Christopher Webber;C. Musgrave;Shunyan Gu;Grayson Johnson;D. Dickie;S. Chabbra
本文报道了两种钴配合物（6-FP）Co(NO3)2(1) （6-FP = 8,8′-（1,2-苯基）二喹啉）和（5-FP）Co(NO3)2(2) （5-FP = 1,2-双（n -7-偶氮苯）苯）的合成、表征和电催化水氧化活性，这两种钴配合物含有氮原子供体的“盖顶芳烃”双齿配体。将钴配合物1和2通过π -π堆叠负载在有序介孔碳（OMC）上，分别得到6- fp - co -OMC-1和5- fp - co -OMC-2异质钴材料，并研究了电催化水氧化的性能。我们发现，当电流密度为10 mA cm -2时，6- fp - co - omc -1的过电位为355 mV，在pH值为14.6时，过电位为400 mV时，转换频率（TOF）为0.53 s -1。fp - co - omc -1的活性是5- fp - co - omc -2的1.6倍，在400 mV过电位下，TOF为0.32 s -1。利用x射线吸收光谱对OMC上的分子络合物进行分析，证明了6- fp -Co-OMC-1的单原子Co位点的结构稳定性，但催化剂活性的缓慢降解可归因于最终形成的Co氧化物簇。以分子络合物为模型的电催化水氧化的DFT计算提供了催化机理的描述。这些研究表明O-O键形成的机制涉及中间的CoIVoxo复合物，该复合物经历分子内还原O-O偶联形成CoII-OOH物种。此外，计算预测分子6-FP-Co结构对电催化水氧化的活性比5-FP-Co更强，这与6-FP-Co- omc -1和5-FP-Co- omc -2的实验研究一致，突出了配体结构影响负载分子催化剂催化活性的可能性。
We report the synthesis, characterization, and electrocatalytic water oxidation activity of two cobalt complexes, (6-FP)Co(NO3)2(1) (6-FP = 8,8′-(1,2-phenylene)diquinoline) and (5-FP)Co(NO3)2(2) (5-FP = 1,2-bis(N-7-azaindolyl)benzene), containing “capping arene” bidentate ligands with nitrogen atom donors. The cobalt complexes1and2were supported on ordered mesoporous carbon (OMC) by π–π stacking, resulting in heterogenized cobalt materials6-FP-Co-OMC-1and5-FP-Co-OMC-2, respectively, and studied for electrocatalytic water oxidation. We find that6-FP-Co-OMC-1exhibits an overpotential of 355 mV for a current density of 10 mA cm–2and a turnover frequency (TOF) of ∼0.53 s–1at an overpotential of 400 mV at pH 14.6-FP-Co-OMC-1exhibits activity that is ∼1.6 times that of5-FP-Co-OMC-2, which gives a TOF of 0.32 s–1at 400 mV overpotential. The structural stability of the single-atom Co site was demonstrated for6-FP-Co-OMC-1using X-ray absorption spectroscopy for the molecular complex supported on OMC, but slow degradation in catalyst activity can be attributed to eventual formation of Co oxide clusters. DFT computations of electrocatalytic water oxidation using the molecular complexes as models provide a description of the catalytic mechanism. These studies reveal that the mechanism for O–O bond formation involves an intermediate CoIVoxo complex that undergoes an intramolecular reductive O–O coupling to form a CoII–OOH species. Further, the calculations predict that the molecular 6-FP-Co structure is more active for electrocatalytic water oxidation than 5-FP-Co, which is consistent with experimental studies of6-FP-Co-OMC-1and5-FP-Co-OMC-2, highlighting the possibility that the ligand structure influences the catalytic activity of the supported molecular catalysts.