Cobalt-Porphyrin Catalyzed Electrochemical Reduction of Carbon Dioxide in Water. 2. Mechanism from First Principles
Cobalt-Porphyrin Catalyzed Electrochemical Reduction of Carbon Dioxide in Water. 2. Mechanism from First Principles
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DOI：
10.1021/jp1012335
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发表时间：
2010-09-23
影响因子：
2.9
通讯作者：
Shelnutt, John A.
中科院分区：
文献类型：
--
作者：
Leung, Kevin;Nielsen, Ida M. B.;Shelnutt, John A.
本文应用第一性原理计算技术，分析了以卟啉钴为催化剂，双电子多步电化学还原水中CO2为CO的过程。密度泛函理论计算与杂化泛函和介质连续溶剂化被用来确定步骤，其中电子被添加。这一信息在明确的水环境中得到从头算分子动力学模拟的证实，揭示了水在稳定二氧化碳与钴结合形成的关键中间体中的关键作用。通过平均力势计算，发现中间体在pH < 9.0时自发接受质子形成羧酸基团，随后C-OH键的裂解形成CO是放热的，并伴有小的自由能势垒。这些预测表明，如果电子向催化剂的转移足够快，所提出的反应机制是可行的。强调了键断过程中钴离子电荷和自旋态的变化、钴三维轨道的DFT+U处理以及电化学电位计算的必要性。
We apply first principles computational techniques to analyze the two-electron, multistep, electrochemical reduction of CO2 to CO in water using cobalt porphyrin as a catalyst. Density functional theory calculations with hybrid functionals and dielectric continuum solvation are used to determine the steps at which electrons are added. This information is corroborated with ab initio molecular dynamics simulations in an explicit aqueous environment which reveal the critical role of water in stabilizing a key intermediate formed by CO2 bound to cobalt. By use of potential of mean force calculations, the intermediate is found to spontaneously accept a proton to form a carboxylate acid group at pH < 9.0, and the subsequent cleavage of a C-OH bond to form CO is exothermic and associated with a small free energy barrier. These predictions suggest that the proposed reaction mechanism is viable if electron transfer to the catalyst is sufficiently fast. The variation in cobalt ion charge and spin states during bond breaking, DFT+U treatment of cobalt 3d orbitals, and the need for computing electrochemical potentials are emphasized.