Through-Space Charge Interaction Substituent Effects in Molecular Catalysis Leading to the Design of the Most Efficient Catalyst of CO2-to-CO Electrochemical Conversion
Through-Space Charge Interaction Substituent Effects in Molecular Catalysis Leading to the Design of the Most Efficient Catalyst of CO2-to-CO Electrochemical Conversion
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DOI：
10.1021/jacs.6b07014
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发表时间：
2016-12-28
影响因子：
15
通讯作者：
Saveant, Jean-Michel
中科院分区：
文献类型：
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作者：
Azcarate, Iban;Costentin, Cyrille;Saveant, Jean-Michel
本研究的出发点是通过空间取代基对铁（0）四苯基卟啉电化学转化CO2-到CO的催化作用的影响，通过结构电子效应和我们分别建立的铁（I/0）标准电位之间的线性自由能相关。四个带正电荷的三甲基苯胺基团的四苯基卟啉（TPP）苯基的帕拉的引入结果在一个重要的正偏离的相关性和催化塔菲尔图的平行改善。这种催化增强效应归因于这些正电荷与由初始Fe-0-CO2加合物携带的负电荷的库仑相互作用，这通过当四个正电荷被也安装在TPP苯基的帕拉上的磺酸酯基团携带的四个负电荷替代时观察到的负偏差来证实。当在TPP苯基的邻位引入四个带正电荷的三甲基苯胺鎓基团时，通过初始Fe-0-CO2加合物的库仑稳定化的这种催化增强策略达到高潮。加入大浓度的弱酸-苯酚-有助于裂解CO2的一个C-O键。所得催化剂的效率是前所未有的，这可以通过用电化学CO2至CO转化的所有目前可用的催化剂的催化塔菲尔图基准来判断。最大转换频率（TOF）高达10（6）s（-1），并且在超电位仅为220 mV时达到;超电位为零时的外推TOF大于300 s（-1）。该催化剂导致CO的高度选择性形成（几乎100%），尽管存在高浓度的苯酚，这可能有利于H-2的释放。它也是非常稳定的，在电解超过80小时后没有显示出明显的变化。
The starting point of this study of through-space substituent effects on the catalysis of the electrochemical CO2-to-CO conversion by iron(0) tetraphenylporphyrins is the linear free energy correlation between through structure electronic effects and the iron(I/0) standard potential that we established separately. The introduction of four positively charged trimethylanilinium groups at the para positions of the tetraphenylporphyrin (TPP) phenyls results in an important positive deviation from the correlation and a parallel improvement of the catalytic Tafel plot. The assignment of this catalysis boosting effect to the Coulombic interaction of these positive charges with the negative charge borne by the initial Fe-0-CO2 adduct is confirmed by the negative deviation observed when the four positive charges are replaced by four negative charges borne by sulfonate groups also installed in the para positions of the TPP phenyls. The climax of this strategy of catalysis boosting by means of Coulombic stabilization of the initial Fe-0-CO2 adduct is reached when four positively charged trimethylanilinium groups are introduced at the ortho positions of the TPP phenyls. The addition of a large concentration of a weak acid-phenol-helps by cleaving one of the C-O bonds of CO2. The efficiency of the resulting catalyst is unprecedented, as can be judged by the catalytic Tafel plot benchmarking with all presently available catalysts of the electrochemical CO2-to-CO conversion. The maximal turnover frequency (TOF) is as high as 10(6) s(-1) and is reached at an overpotential of only 220 mV; the extrapolated TOF at zero overpotential is larger than 300 s(-1). This catalyst leads to a highly selective formation of CO (practically 100%) in spite of the presence of a high concentration of phenol, which could have favored H-2 evolution. It is also very stable, showing no significant alteration after more than 80 h of electrolysis.