Metal–nitrogen–carbon (M–N–C) single-atom catalysts (SACs) have emerged as promising heterogeneous electrocatalysts for the CO₂ reduction reaction (CO₂RR). However, the predominant production of CO over multielectron products remains a challenge for most M–N–C SACs, with the exception of cobalt phthalocyanine (CoPc). In this study, the comparison of CoPc and a series of analogous M–N–C SACs was systematically investigated using density functional theory calculations to unravel the factors contributing to the selectivity of CoPc in catalyzing multielectron CO₂RR. The relationship between the selectivity and the electronic configuration of M–N–C SACs was revealed. The half-filled d_z² orbital of the cobalt ion lead to moderate chemisorption of *CO on CoPc, enabling the subsequent protonation of *CO. In addition, we identified a unique type of hydrogen bond in which the C atom of *CO acts as the proton acceptor (C···H–O hydrogen bond), which significantly promotes the proton transfer to *CO and selectivity for multielectron products. Only the *CO on CoPc was observed to form the C···H–O hydrogen bond, elucidating the unique multielectron CO₂RR performance of CoPc. In addition, we further elucidated the formation mechanism of the C···H–O hydrogen bond, which provides an alternative strategy to accelerate proton transfer in electrochemical reactions by utilizing this unconventional hydrogen bond.

中文翻译：

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了解钴酞菁在二氧化碳多电子还原中的独特选择性


金属-氮-碳 （M-N-C） 单原子催化剂 （SAC） 已成为 CO₂ 还原反应 （CO₂RR） 的有前途的非均相电催化剂。然而，对于大多数 M-N-C SAC 来说，CO的主要生产仍然是一个挑战，钴酞菁 （CoPc） 除外。在这项研究中，使用密度泛函理论计算系统研究了 CoPc 与一系列类似 M-N-C SACs 的比较，以揭示影响 CoPc 催化多电子 CO₂RR 选择性的因素。揭示了 M-N-C SAC 的选择性与电子构型之间的关系。钴离子的半填充 d_z² 轨道导致 *CO 在 CoPC 上适度化学沉淀，从而能够随后实现 *CO 的质子化。此外，我们还确定了一种独特的氢键类型，其中 *CO 的 C 原子充当质子受体 （C···H-O 氢键），它显着促进质子向 *CO 的转移和多电子产物的选择性。仅观察到 CoPc 上的 *CO 形成 C···H-O 氢键，阐明了 CoPc 独特的多电子 CO₂RR 性能。此外，我们进一步阐明了 C···H-O 氢键，它提供了一种替代策略，通过利用这种非常规氢键来加速电化学反应中的质子转移。