Two types of single metal atoms embedded in graphene were investigated as a potential electrocatalyst for oxygen reduction reaction (ORR) for the application in a fuel cell. ORR was considered in the four elementary reaction steps of oxygen hydrogenation, perhydroxyl production, atomic oxygen hydrogenation, and final water form. All calculations of catalytic activity were performed with the Vienna Ab Initio Simulation Package (VASP) on an M@Gra (M = Mn, Fe, Co, and Ir)–embedded structure, indicating that high-efficiency catalytic activity in the oxidation reaction takes place on the top of metal atom sites. Our calculations revealed that ORR is profiled via four-electron transfer pathway. Activity of these catalysts is closely related to the same scaling linear relations between the adsorption energies of the ORR intermediates on different catalytic surfaces; this can improve their catalytic activity for O₂ reduction through a high-efficiency 4e reaction path. Mn- and Ir-doped of cell A graphene exhibited excellent ORR catalytic performance in case of their small overpotential (less than 0.23 V) and low-energy barrier (less than 0.64 eV) of the Ir-doped graphene rate-determining step. Mn@Gra and Fe@Gra of cell B monolayers showed poor ORR catalytic performance due to the strong interaction between various ORR-involved species. Based on the free energy change and activation energy of each intermediate reaction in ORR, Fe@Gra and Ir@Gra are promising catalysts for ORR processes in fuel cells. This provides useful guidance for different types of catalysts in applications to fuel cells.

Graphical Abstract

研究了嵌入石墨烯中的两种类型的单金属原子，作为用于燃料电池中的氧还原反应（ORR）的潜在电催化剂。在氧加氢，过羟基生成，原子氧加氢和最终水形式的四个基本反应步骤中考虑了ORR。所有催化活性的计算均使用Vienna Ab Initio模拟程序包（VASP）在M @ Gra（M = Mn，Fe，Co和Ir）嵌入式结构上进行，这表明氧化反应中的高效催化活性放置在金属原子部位的顶部。我们的计算表明，ORR通过四电子转移途径进行了分析。这些催化剂的活性与ORR中间体在不同催化表面上的吸附能之间相同的比例线性关系密切相关。这可以提高它们对O的催化活性通过高效的4e反应路径进行₂还原。Mn和Ir掺杂的电池A石墨烯在Ir掺杂的石墨烯速率测定步骤中的过小电势（小于0.23 V）和低能垒（小于0.64 eV）的情况下表现出出色的ORR催化性能。B细胞单层的Mn @ Gra和Fe @ Gra显示出较差的ORR催化性能，这是由于各种ORR涉及的物种之间的强相互作用。基于ORR中每个中间反应的自由能变化和活化能，Fe @ Gra和Ir @ Gra是用于燃料电池ORR过程的有前途的催化剂。这为在燃料电池中应用的不同类型的催化剂提供了有用的指导。

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