Ganyecz Ádám, Kállay Mihály
Department of Physical Chemistry and Materials Science, Budapest University of Technology and Economics, P.O.Box 91, Budapest H-1521, Hungary.
J Phys Chem C Nanomater Interfaces. 2021 Apr 29;125(16):8551-8561. doi: 10.1021/acs.jpcc.0c11340. Epub 2021 Apr 20.
The goal of this study is to provide insight into the mechanism of the oxygen reduction reaction (ORR) on N-doped graphene surfaces. Using density functional theory and a computational hydrogen electrode model, we studied the energetics of the ORR intermediates, the effect of the position of the reaction site, and the effect of the position of the N modification relative to the active site on model graphene surfaces containing one or two N atoms. We found that scaling relations can be derived for N-doped graphenes as well, but the multiplicity of the surface should be taken into account. On the basis of the scaling relations between intermediates OOH* and OH*, the minimal overpotential is 0.33 V. Analysis of the data showed that N atoms in the meta position usually decrease the adsorption energy, but those in the ortho position aid the adsorption. The outer position on the zigzag edge of the graphene sheet also promotes the adsorption of oxygenated species, while the inner position hinders it. Looking at the most effective active sites, our analysis shows that the minimal overpotential can be approached with various doping arrangements, which also explains the contradicting results in the literature. The dissociative pathway was also investigated, but we found only one possible active site; therefore, this pathway is not really viable. However, routes not preferred thermodynamically pose the possibility of breaking the theoretical limit of the overpotential of the associative pathway.
本研究的目标是深入了解氮掺杂石墨烯表面上氧还原反应（ORR）的机制。使用密度泛函理论和计算氢电极模型，我们研究了ORR中间体的能量学、反应位点位置的影响以及相对于活性位点的氮修饰位置对含有一个或两个氮原子的模型石墨烯表面的影响。我们发现，对于氮掺杂石墨烯也可以推导出标度关系，但应考虑表面的多重性。基于中间体OOH和OH之间的标度关系，最小过电位为0.33V。数据分析表明，间位的氮原子通常会降低吸附能，而邻位的氮原子则有助于吸附。石墨烯片之字形边缘的外侧位置也促进了含氧物种的吸附，而内侧位置则起到阻碍作用。查看最有效的活性位点，我们的分析表明，通过各种掺杂排列可以接近最小过电位，这也解释了文献中相互矛盾的结果。我们还研究了解离途径，但只发现了一个可能的活性位点；因此，这条途径实际上并不可行。然而，热力学上不太有利的途径可能会突破缔合途径过电位的理论极限。
