Catalysis of the electrochemical reduction of carbon dioxide by iron(0) porphyrins. Synergistic effect of Lewis acid cations
Catalysis of the electrochemical reduction of carbon dioxide by iron(0) porphyrins. Synergistic effect of Lewis acid cations
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DOI：
10.1021/jp9618486
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发表时间：
1996-12-19
影响因子：
--
通讯作者：
Saveant, JM
中科院分区：
文献类型：
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作者：
Bhugun, I;Lexa, D;Saveant, JM
添加刘易斯酸阳离子如Mg 2+、Ca 2+、Ba 2+、Li+和Na+在催化效率和催化剂寿命两方面显著改善了铁（0）四苯基卟啉对CO2还原的催化作用。一氧化碳是主要产物，而甲酸盐的形成程度较低（Mg 2+为30%，Li+仅为10%）。循环伏安法测定表明，这些刘易斯酸增效剂的活性顺序为Mg ~（2+）与Ca ~（2+）一致> Ba ~（2+）> Li ~+ > Na ~+。动力学的系统分析允许的二价和一价阳离子的效果的机制的建议。在许多情况下，辅助催化是如此之强，以至于电流受到产物抑制的影响，如先前用布朗斯台德酸增效剂观察到的。在本例中，自我抑制更不可逆，需要采用不同的方法进行分析。推拉机制在催化CO2还原中的重要性因此得到证实;电子被富电子催化剂推入CO2分子中，并且缺电子的催化剂的存在有助于C-O键之一的断裂。
Addition of Lewis acid cations such as Mg2+, Ca2+, Ba2+, Li+ and Na+ considerably improves the catalysis of CO2 reduction by iron(0) tetraphenylporphyrins, in terms of both catalytic efficiency and lifetime of the catalyst. Carbon monoxide is the main product, while formate is formed to a lesser extent (30% with Mg2+ and only 10% with Li+). Cyclic voltammetry indicates that the order of reactivity of these Lewis acid synergists is Mg2+ congruent to Ca2+ > Ba2+ > Li+ > Na+. Systematic analysis of the kinetics allows the proposal of a mechanism for the effect of both the divalent and monovalent cations. In many instances, the assisted catalysis is so strong that the current is affected by product inhibition as observed previously with Bronsted acid synergists. Self-inhibition is more irreversible in the present case and required a different approach to be analyzed. The importance of push-pull mechanisms in the catalysis of CO2 reduction is thus confirmed; electrons are pushed into the CO2 molecule by the electron-rich catalyst and the cleavage of one of the C-O bonds is helped by the presence of an electron deficient synergist.