Understanding the Selectivity of the Oxygen Reduction Reaction at the Atomistic Level on Nitrogen‐Doped Graphitic Carbon Materials

Abstract

The oxygen reduction reaction (ORR) is of paramount interest, in the context of both alternative energy applications in fuel cells and for on‐site hydrogen peroxide (H2O2) production in environmental remediation applications. Using theoretical and experimental methods, the mechanism involved in the ORR is studied on nitrogen‐doped graphitic carbon materials. The two principal reaction pathways involved in the ORR are the four‐electron pathway producing water (H2O), or the two‐electron pathway leading to the formation of H2O2. An atomistic step by step ORR mechanism is proposed to understand the selectivity of the reaction toward the two principal pathways. The results show that graphitic N sites favor the two‐electron pathway, in a similar way to three pyridinic N sites. Meanwhile, the one or two pyridinic N sites lead to the four‐electron pathway. The calculations show the importance of dangling bonds and/or pentagonal C rings in selectivity toward the four‐electron pathway. The results are consistent with recent reports on the importance of topological defects in graphitic carbon materials. The understanding of the ORR mechanism is very important for the design and development of novel ORR electrocatalysts to favor the required pathway, according to the application.

Engineering Synergistic Edge‐N Dipole in Metal‐Free Carbon Nanoflakes toward Intensified Oxygen Reduction Electrocatalysis

“…It has been reported that the pyridinic-N/graphitic-N ratio of N-doped carbons could be modified via annealing due to their stability discrepancy at high temperatures. [46][47][48] NCF was further annealed at 1000 °C under Ar atmosphere to get N-modified NCF-1000 with N content of 1.82 wt%. As shown in Figure S13, Supporting Information, NCF-1000 still maintains highly graphitic structure, but the pyridinic-N/graphitic-N ratio changes from 0.61 in NCF to 0.35.…”

“…[6][7][8][9][10] Along with intensive and in-depth study, the intrinsic topological defects and edges in metal-free nanocarbons have also been distinguished as the origin of ORR activity. [11][12][13][14][15][16][17][18][19][20][21] Despite the striking progresses, the conclusions on the accurate structures of ORR active sites remain controversial and even conflicting, particularly for specific configuration of the pivotal N dopants (pyridinic-N versus graphitic-N). [22][23][24][25][26][27][28] For example, based on a N-doped highly-oriented pyrolytic graphite (HOPG) model catalyst, the ORR activity is connected to the presence of pyridinic-N. [24] While study on a series of controlled N-doped carbons reveals the graphitic-N exclusively catalyzes ORR in both alkaline and acidic media, and pyridinic-N has negligible ORR activity.…”

Red Bean Pod Derived Heterostructure Carbon Decorated with Hollow Mixed Transition Metals as a Bifunctional Catalyst in Zn‐Air Batteries

“…The presence of graphitic N modulates the electronic distribution on the adjacent carbon atoms, which facilitates better absorption of oxygen [44] . Meanwhile, pyridinic N prefers to occupy the defect site or the edge of carbon, serving as the active sites to facilitate ORR via a four‐electron pathway [45] …”

Ultra-Stable Potassium Ion Storage of Nitrogen-Doped Carbon Nanofiber Derived from Bacterial Cellulose

“…In addition, we also provide the high-resolution N 1 s XPS spectrum of N-CNF to further confirm the nitrogen doping. It is found that the N 1 s XPS spectrum can be deconvoluted into four peaks at 398.4, 400.0, 401.1 and 403.5 eV, corresponding to the pyridinic N, pyrrolic N, graphitic N and oxidized-N, respectively [ 48 , 49 , 50 , 51 ]. Among them, it is observed that the peak at 398.4 presents more strongly than other peaks, indicating that the nitrogen doping in N-CNF mainly constitutes pyridinic N. In addition, we also provide the nitrogen adsorption–desorption isotherms and pore size distributions of CNF and N-CNF, as shown in Figure S2 .…”