Electrochemical CO₂ reduction (CO₂R) to feedstocks competes with the hydrogen evolution reaction (HER). Cobalt phthalocyanine (CoPc) immobilized onto carbon driven by π–π interaction represents a classical type of heterogeneous molecular catalyst for CO₂R. However, the impacts of π conjugation on the electrocatalysis have not been clarified. Herein, the electrochemical properties of CoPc were investigated by comparison of its analogue to 2,3-naphthalocyanine cobalt (NapCo) having extended π conjugation. It is found that CoPc is redox-active on carbon to provide low oxidized Co sites for improving the CO₂R activity and selectivity, while NapCo on carbon turned out to be redox-inert leading to lower performance. In addition, the redox-mediated mechanism for CO₂R on CoPc tends to operate with increasing electrolyte alkalinity, which further enhances the reaction selectivity. We speculated that moderate π conjugation allows the redox-mediated mechanism on CoPc, which is critical to promote CO₂R performance while depressing the competing HER.

中文翻译：

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深入了解 π-π 组装对基于酞菁的异质分子电催化的影响

原料的电化学CO ₂还原(CO ₂ R) 与析氢反应(HER) 竞争。由π-π相互作用驱动的固定在碳上的钴酞菁（CoPc）代表了一种经典类型的CO ₂ R多相分子催化剂。然而，π共轭对电催化的影响尚未阐明。在此，通过将 CoPc 的类似物与具有扩展 π 共轭的 2,3-萘酞菁钴 (NapCo) 进行比较，研究了 CoPc 的电化学性质。发现CoPc在碳上具有氧化还原活性，以提供低氧化Co位点以提高CO ₂ R活性和选择性，而碳上的NapCo被证明是氧化还原惰性的，导致性能较低。此外，CoPc上CO ₂ R的氧化还原介导机制往往随着电解质碱度的增加而起作用，这进一步提高了反应选择性。我们推测，适度的 π 共轭可以在 CoPc 上实现氧化还原介导的机制，这对于促进 CO ₂ R 性能同时抑制竞争性 HER 至关重要。