A direct four-electron process on Fe–N₃ doped graphene for the oxygen reduction reaction: a theoretical perspective

Abstract

The reaction mechanism for the ORR on Fe–N3-Gra is investigated theoretically. Our results indicate that the ORR is a direct four-electron process, and the kinetically most favorable pathway is O2 hydrogenation.

Effect of nitrogen-doping configuration in graphene on the oxygen reduction reaction

“…However, continuing efforts have also studied other elements for doping such as phosphorous, sulfur, halogen group atoms, iron, and co-doping in many elds. [13][14][15][16][17][18][19][20] By now, it has been reported, both experimentally and computationally, that NG and carbon defects can facilitate ORR on the cathode in fuel cells. Nitrogen-doped carbon materials have shown excellent performance in this regard.…”

Identifying Iron–Nitrogen/Carbon Active Structures for Oxygen Reduction Reaction under the Effect of Electrode Potential

“…However, active-site identification is a well known hard job due to the noncrystalline nature of TM–N/C catalysts. For the Fe–N/C catalyst, by combining theoretical modeling with advanced characterizations such as the extended X-ray absorption fine structure (EXAFS) and Mössbauer spectroscopy, , 11 moieties have been proposed to date. ,− These moieties could all exist in the practical Fe–N/C catalysts and work simultaneously under the same conditions. Nearly every moiety was claimed to be highly active according to the respective theoretical modeling.…”

“…The four-N-coordinated Fe (FeN 4 C 10 ) moiety has been regarded as the active site for ORR due to its structural similarity to the macrocyclic molecules of phthalocyanine and porphyrin with considerable ORR activity. , Recently, it has been found that changing the coordination environment of the Fe atoms can effectively tune the ORR activity of the Fe–N/C electrocatalysts. Dodelet and Guo et al suggested that the two-N-coordinated Fe (FeN 2 C 12 ) is more likely to promote the 4 e ORR to H 2 O, whereas the FeN 4 C 10 contributes more to the 2 e ORR to H 2 O 2 . , The three-N-coordinated Fe (FeN 3 C 9 ) was shown to be more easily formed and have better stability than FeN 4 C 10 . , Moreover, the five-coordinated Fe centers, which are FeN 4 attached by different ligands, have attracted more and more attention due to the greatly expanded space to tune the properties of Fe centers. Chen et al engrafted different heterocyclic molecules to the in-plane FeN 4 and obtained structures of FeN 4 IM (IM = imidazole), FeN 4 PY (PY = pyridine), and FeN 4 NHC (NHC = N-heterocyclic carbene), as shown in Figure g–i .…”

Theoretical Insights into Enhanced Electrocatalytic Activity of Oxygen Reduction Reactions on N/S-Codoped Graphene Quantum Dots

“…Many theoretical studies have shown that the end-on mode is easier to occur. Hence, we consider only the end-on mode in this study. , In the beginning, O 2 molecules adsorb on the active sites and then O 2 is protonated to form OOH, O, OH, and H 2 O sequentially. Based on the above analysis for the charge and spin density distribution of doped GQDs, the adsorption energy and structures of O 2 on the studied doped GQDs are shown in Figure .…”