Competence Centre for Catalysis and Department of Applied Physics, Chalmers University of Technology , SE-412 96, Göteborg, Sweden.
J Am Chem Soc. 2014 Jan 29;136(4):1320-6. doi: 10.1021/ja4060299. Epub 2014 Jan 13.
Bioinspired structures are promising as improved catalysts for various redox reactions. One example is metal hangman-porphyrines (MHP), which recently have been suggested for oxygen reduction/evolution reaction (ORR/OER). The unique properties of the MHPs are attributed to both the hangman scaffold and the C6F5 side groups. Herein, the OER/ORR over various transition metal MHPs is investigated by density functional theory calculations within an electrochemical framework. A comparison of the reaction landscape for MHP, metal porphyrine (MP) and metaltetrafluorophenyloporphyrines (MTFPP), allow for a disentanglement of the different roles of the hangman motif and the side groups. In agreement with experimental studies, it is found that Fe and Co are the best MHP metal centers to catalyze these reactions. We find that the addition of the three-dimensional moiety in the form of hangman scaffold does not break the apparently universal energy relation between *OH and *OOH intermediates. However, the hangman motif is found to stabilize the oxygen intermediate, whereas addition of C6F5 groups reduces the binding energy of all reaction intermediates. Our results indicate that the combination of these two effects allow new design possibilities for macromolecular systems with enhanced catalytic OER/ORR activity.
受生物启发的结构有望成为各种氧化还原反应的改进型催化剂。金属绞刑吏卟啉（MHP）就是一个例子，它最近被提议用于氧还原/氧析出反应（ORR/OER）。MHP 的独特性质归因于绞刑吏支架和 C6F5 侧基。在此，通过电化学框架内的密度泛函理论计算研究了各种过渡金属 MHP 的 OER/ORR。对 MHP、金属卟啉（MP）和金属五氟苯基卟啉（MTFPP）的反应势垒的比较，可以解开绞刑吏模体和侧基的不同作用。与实验研究一致，发现 Fe 和 Co 是催化这些反应的最佳 MHP 金属中心。我们发现，以绞刑吏支架的形式添加三维部分不会打破OH 和OOH 中间体之间显然普遍的能量关系。然而，发现绞刑吏模体稳定氧中间体，而添加 C6F5 基团会降低所有反应中间体的结合能。我们的结果表明，这两种效应的结合为具有增强的催化 OER/ORR 活性的大分子系统提供了新的设计可能性。
