Electrochemical conversion of carbon monoxide, a major one-carbon product of carbon dioxide reduction, into high-value multi-carbon products is one of the promising strategies to address the overall energy demands and climate change. A lot of efforts have been devoted to the exploration of highly efficient catalysts for the formation of single carbon products. However, further reduction to more reduced products is hampered by high energy barriers for C−C bond formation and low selectivity of the products. Herein, the potential of homo-bimetallic and hetero-bimetallic complexes of previously established expanded twin porphyrin (H₄L) ligand, also known as conjoined-twin porphyrin (CTP) ligand, towards the reduction of CO to valued commodity chemicals is systematically investigated by using density functional theory (DFT) computations. In these complexes, the presence of two metal atoms in the N4 pockets enhances the chances of coupling of two adsorbed CO molecules, thus facilitating the formation of C−C bond formation. The results reveal that both the dicobalt and cobalt nickel complex of conjoined-twin porphyrin ligand show high activity and selectivity towards the conversion of CO to ethanol with a limiting potential of only −0.59 V and −0.61 V, respectively. The narrow band gap and shallower d band centre could be attributed to the potential cause for the enhanced activity of Co containing complexes. Moreover, these complexes displayed high thermal stability, thus acts as potential candidates for experimental exploration. Our results offer a promising alternative to traditional Cu-based electrocatalysts for the formation of C2 products.

中文翻译：

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一种高效的基于双联卟啉的络合物，用于将CO电化学还原为乙醇

一氧化碳（一种主要的减少二氧化碳的碳产品）电化学转化为高价值的多碳产品是解决整体能源需求和气候变化的有前途的策略之一。已经进行了许多努力来探索用于形成单碳产物的高效催化剂。但是，由于C-C键形成的高能垒和产物的低选择性阻碍了进一步还原成更多还原产物的过程。本文中，先前建立的双生卟啉（H _4）的均双金属和异双金属配合物的潜力L）配体，也称为连双卟啉（CTP）配体，旨在通过使用密度泛函理论（DFT）计算系统地研究将CO还原为有价值的商品化学品。在这些络合物中，N4口袋中两个金属原子的存在增加了两个吸附的CO分子偶联的机会，从而促进了CC键的形成。结果表明，双-双卟啉配体的二钴和钴镍配合物均表现出高的活性和选择性，对CO转化为乙醇的极限电势分别仅为-0.59 V和-0.61V。窄的带隙和较浅的d带中心可归因于含Co配合物活性增强的潜在原因。而且，这些配合物显示出很高的热稳定性，因此可以作为实验探索的潜在候选者。我们的结果为形成C2产品提供了一种有希望的替代传统铜基电催化剂的方法。