Templating Bicarbonate in the Second Coordination Sphere Enhances Electrochemical CO2 Reduction Catalyzed by Iron Porphyrins,Journal of the American Chemical Society

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Templating Bicarbonate in the Second Coordination Sphere Enhances Electrochemical CO2 Reduction Catalyzed by Iron Porphyrins
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2022-06-24 , DOI: 10.1021/jacs.2c02972
Jeffrey S Derrick _{1,

2} , Matthias Loipersberger ₁ , Sepand K Nistanaki ₁ , Aila V Rothweiler ₁ , Martin Head-Gordon _{1,

2} , Eva M Nichols ₃ , Christopher J Chang _{1,

2,

4}

Affiliation

Bicarbonate-based electrolytes are ubiquitous in aqueous electrochemical CO₂ reduction, particularly in heterogenous catalysis, where they demonstrate improved catalytic performance relative to other buffers. In contrast, the presence of bicarbonate in organic electrolytes and its roles in homogeneous electrocatalysis remain underexplored. Here, we investigate the influence of bicarbonate on iron porphyrin-catalyzed electrochemical CO₂ reduction. We show that bicarbonate is a viable proton donor in organic electrolyte (pK_a = 20.8 in dimethyl sulfoxide) and that urea pendants in the second coordination sphere can be used to template bicarbonate in the vicinity of a molecular iron porphyrin catalyst. The templated binding of bicarbonate increases its acidity, resulting in a 1500-fold enhancement in catalytic rates relative to unmodified parent iron porphyrin. This work emphasizes the importance of bicarbonate speciation in wet organic electrolytes and establishes second-sphere bicarbonate templating as a design strategy to harness this adventitious acid and enhance CO₂ reduction catalysis.

中文翻译：

在第二配位球中模板化碳酸氢盐可增强铁卟啉催化的电化学 CO2 还原

基于碳酸氢盐的电解质普遍存在于水性电化学 CO ₂还原中，特别是在多相催化中，它们相对于其他缓冲液表现出更高的催化性能。相比之下，有机电解质中碳酸氢盐的存在及其在均相电催化中的作用仍未得到充分探索。在这里，我们研究了碳酸氢盐对铁卟啉催化的电化学 CO ₂还原的影响。我们表明碳酸氢盐是有机电解质中可行的质子供体（p K _a= 20.8 在二甲亚砜中），并且第二配位层中的尿素侧基可用于在分子铁卟啉催化剂附近作为碳酸氢盐的模板。碳酸氢盐的模板化结合增加了其酸度，导致催化速率相对于未修饰的母体铁卟啉提高了 1500 倍。这项工作强调了碳酸氢盐形态在湿有机电解质中的重要性，并建立了第二球碳酸氢盐模板作为利用这种外来酸和增强 CO ₂还原催化的设计策略。

更新日期：2022-06-24

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