From non-innocent to guilty: on the role of redox-active ligands in the electro-assisted reduction of CO2 mediated by a cobalt(II)-polypyridyl complex,Sustainable Energy & Fuels

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From non-innocent to guilty: on the role of redox-active ligands in the electro-assisted reduction of CO2 mediated by a cobalt(II)-polypyridyl complex
Sustainable Energy & Fuels ( IF 5.0 ) Pub Date : 2020-05-13 , DOI: 10.1039/d0se00570c
N. Queyriaux _{1,

2,

3,

4,

5} , K. Abel _{1,

2,

3,

4,

5} , J. Fize _{6,

7,

8,

9,

10} , J. Pécaut _{6,

7,

8,

9,

11} , M. Orio _{7,

12,

13,

14,

15} , L. Hammarström _{1,

2,

3,

4,

5}

Affiliation

The electrochemical behavior of [Co(bapbpy)Cl]⁺ [1-Cl]⁺, a pentacoordinated polypyridyl cobalt(II) complex containing a redox-active tetradentate ligand (bapbpy: 6,6′-bis-(2-aminopyridyl)-2,2′-bipyridine) has been investigated in DMF. Cyclic voltammograms (CV), recorded in the presence of increasing amounts of chloride anions, highlighted the existence of an equilibrium with the neutral hexacoordinated complex. Under a CO₂ atmosphere, CVs of [Co(bapbpy)Cl]⁺ exhibit significant current enhancement assigned to CO₂ catalytic reduction. Controlled-potential electrolysis experiments confirmed formation of CO and HCOOH as the only identifiable products. The addition of water or chloride ions was shown to affect the distribution of the products obtained, as well as the faradaic efficiency associated with their electrocatalytic generation. A combination of electrochemical techniques, chemical reductions, spectroscopic measurements (UV-vis and IR) and quantum chemical calculations suggests that the ability of the bapbpy ligand to be reduced at moderately negative potentials drastically limits the catalytic performances of [1-Cl]⁺, by stabilizing the formation of a catalytically-competent CO₂-adduct that only slowly reacts with oxide acceptors to evolve towards the desired reduction products.

中文翻译：

从无辜到有罪：关于氧化还原活性配体在钴（II）-聚吡啶配合物介导的电辅助还原CO2中的作用

[Co（bapbpy）Cl] ⁺ [ 1-Cl ] ⁺的电化学行为，是一种具有氧化还原活性四齿配体的五配位多吡啶基钴（II）配合物（bapbpy：6,6'-双-（2-氨基吡啶基）- 2,2'-联吡啶已在DMF中进行了研究。在氯离子含量不断增加的情况下记录的循环伏安图（CV）突出显示了与中性六配位络合物的平衡。在CO ₂气氛下，[Co（bapbpy）Cl] ^+的CV表现出显着的电流分配给CO ₂催化还原。电位控制电解实验证实，CO和HCOOH的形成是唯一可识别的产物。结果表明，添加水或氯离子会影响所得产物的分布，以及与其电催化生成相关的法拉第效率。电化学技术，化学还原，光谱测量（紫外可见和红外）和量子化学计算的结合表明，bapbpy配体在中等负电势下的还原能力极大地限制了[ 1-Cl ] ⁺的催化性能，通过稳定催化型CO ₂的形成-仅与氧化物受体缓慢反应的加合物，向所需的还原产物方向发展。

更新日期：2020-06-30

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