Harvey Catherine M, Chardon-Noblat Sylvie, Costentin Cyrille
Université Grenoble Alpes, DCM, CNRS, 38000 Grenoble, France.
J Am Chem Soc. 2025 Jul 9;147(27):24171-24178. doi: 10.1021/jacs.5c09840. Epub 2025 Jun 27.
The electrochemical reduction of CO, coupled with renewable energy, offers a promising approach to convert CO to valuable products. However, the presence of O in operating environments presents challenges such as catalyst degradation. Transition metal complexes, such as iron tetraphenylporphyrin (TPPFe), are molecular electrocatalysts with tunable structures and redox properties that make them attractive for CO reduction. A critical challenge for practical application is achieving O tolerance─the ability of the catalyst to sustain CO reduction without degradation in the presence of O. This study highlights the self-protection mechanism of TPPFe in homogeneous electrocatalysis against O and reactive oxygen species (ROS). Using rotating disk voltammetry, constant potential electrolysis, and spectro-electrochemistry, we demonstrate that lesser reduced TPPFe states selectively reduce O, form a protective layer that shields the active catalyst for CO reduction. Furthermore, we reveal that mass transport significantly influences the efficiency of CO-to-CO conversion in O-containing environments, with stirring rates during electrolysis directly affecting CO faradaic yields. This self-protection mechanism, applicable to other catalysts with multiple redox states and adaptable to molecular catalysts immobilized in thick films, underscores the importance of optimizing mass transport conditions and catalyst design to achieve an O-tolerant CO reduction.
将二氧化碳电化学还原与可再生能源相结合，为将二氧化碳转化为有价值的产品提供了一种很有前景的方法。然而，运行环境中氧气的存在带来了诸如催化剂降解等挑战。过渡金属配合物，如四苯基卟啉铁（TPPFe），是具有可调节结构和氧化还原性质的分子电催化剂，这使得它们对二氧化碳还原具有吸引力。实际应用中的一个关键挑战是实现耐氧性——即催化剂在有氧气存在的情况下持续进行二氧化碳还原而不降解的能力。本研究突出了TPPFe在均相电催化中对氧气和活性氧（ROS）的自我保护机制。通过旋转圆盘伏安法、恒电位电解和光谱电化学方法，我们证明还原程度较低的TPPFe状态会选择性地还原氧气，形成一个保护层，保护用于二氧化碳还原的活性催化剂。此外，我们揭示了传质在含氧化环境中对二氧化碳到一氧化碳转化效率有显著影响，电解过程中的搅拌速率直接影响一氧化碳的法拉第产率。这种自我保护机制适用于其他具有多种氧化还原状态的催化剂，并且适用于固定在厚膜中的分子催化剂，强调了优化传质条件和催化剂设计以实现耐氧性二氧化碳还原的重要性。
