Levell Zachary, Yu Saerom, Wang Ruoyu, Liu Yuanyue
Texas Materials Institute and Department of Mechanical Engineering, The University of Texas at Austin, Austin, Texas 78731, United States.
J Am Chem Soc. 2025 Jan 8;147(1):603-609. doi: 10.1021/jacs.4c12479. Epub 2024 Dec 21.
Single metal atoms embedded in nitrogen-doped graphene (M-N-C) have emerged as a promising catalyst for a wide variety of reactions. In addition to the pyridinic site, there is another site responsible for the catalytic activity, but its structure is under debate. Here, we resolve its structure using first-principles calculations. Using Fe-N-C as a representative example, we systematically explore numerous possible structures and discover a new moiety with comparable energy to the pyridinic. This moiety features a hybrid coordination environment between pyridinic and porphyrinic and is located at the edge of graphene sheets or pores. We further calculate its X-ray absorption spectrum, catalytic thermodynamics for oxygen reduction reaction (ORR), and stability under ORR conditions, all of which support its existence. Lastly, we show that this site also exists in other M-N-C with different M elements. This study uncovers a new and important structure in M-N-C and paves a critical step toward site engineering for improved catalytic performance.
嵌入氮掺杂石墨烯（M-N-C）中的单金属原子已成为用于多种反应的有前景的催化剂。除了吡啶型位点外，还有另一个负责催化活性的位点，但其结构仍存在争议。在此，我们使用第一性原理计算解析其结构。以Fe-N-C为例，我们系统地探索了众多可能的结构，并发现了一种与吡啶型具有相当能量的新部分。该部分具有吡啶型和卟啉型之间的混合配位环境，位于石墨烯片层或孔隙的边缘。我们进一步计算了其X射线吸收光谱、氧还原反应（ORR）的催化热力学以及ORR条件下的稳定性，所有这些都支持其存在。最后，我们表明该位点也存在于其他具有不同M元素的M-N-C中。这项研究揭示了M-N-C中一种新的重要结构，并为通过位点工程提高催化性能迈出了关键一步。
