Electrocatalytic nitrate reduction with Co-based catalysts: comparison of DIM, TIM and cyclam ligands
Electrocatalytic nitrate reduction with Co-based catalysts: comparison of DIM, TIM and cyclam ligands
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钴基催化剂电催化硝酸盐还原：DIM、TIM 和 cyclam 配体的比较
DOI：
10.1039/d1dt02175c
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发表时间：
2021
影响因子：
4
通讯作者：
Jakubikova, Elena
中科院分区：
文献类型：
--
作者：
Kwon, Hyuk-Yong;Braley, Sarah E.;Madriaga, Jose P.;Smith, Jeremy M.;Jakubikova, Elena
在过去的一个世纪里，由于人类活动，全球环境硝酸盐浓度显著增加，造成了饮用水污染和水生缺氧，因此开发有效的硝酸盐还原剂迫在眉睫。本研究比较了三种潜在的基于大环的硝酸盐还原电催化剂：[Co(DIM)]3+, [Co(cyclam)]3+和[Co(TIM)]3+。虽然这三种配合物具有相似的结构，但只有[Co(DIM)]3+被实验确定为选择性硝酸还原生成水中氨的活性电催化剂。在重金属电极上，[Co(cyclam)]3+可将硝酸还原为氨和羟胺，而[Co(TIM)]3+对硝酸还原无活性。作为了解结构和电子性质对硝酸还原高效电催化剂的重要作用的第一步，采用密度泛函理论（DFT）研究了三种Co配合物的电子结构，并根据实验结果校准了还原电位。此外，利用离散傅里叶变换（DFT）探讨了硝酸还原第一步的四种不同反应机理。计算出的反应势垒揭示了氧化还原非无害复合物中的电子转移、底物结合和分子内氢键的组合如何决定了co基催化剂对硝酸盐还原的活性。
Over the past century, the global concentration of environmental nitrate has increased significantly from human activity, which has resulted in the contamination of drinking water and aquatic hypoxia around the world, so the development of effective nitrate-reducing agents is urgent. This work compares three potential macrocycle-based nitrate reduction electrocatalysts: [Co(DIM)]3+, [Co(cyclam)]3+ and [Co(TIM)]3+. Although all three complexes have similar structures, only [Co(DIM)]3+ has been experimentally determined to be an active electrocatalyst for selective nitrate reduction to produce ammonia in water. While [Co(cyclam)]3+ can reduce aqueous nitrate to ammonia and hydroxylamine at heavy metal electrodes, [Co(TIM)]3+ is inactive for the reduction of nitrate. As an initial step to understanding what structural and electronic properties are important for efficient electrocatalysts for nitrate reduction, density functional theory (DFT) was employed to investigate the electronic structure of the three Co complexes, with the reduction potentials calibrated to experimental results. Moreover, DFT was employed to explore four different reaction mechanisms for the first steps of nitrate reduction. The calculated reaction barriers reveal how a combination of electron transfer in a redox non-innocent complex, substrate binding, and intramolecular hydrogen bonding dictates the activity of Co-based catalysts toward nitrate reduction.