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

Abstract

Nitrogen doping represents an effective way to induce charge/spin polarization in nanocarbons for promoting oxygen reduction reaction (ORR) activity. However, it remains elusive to define the dominant active sites with respect to two critical N-configurations of pyridinic-N and graphitic-N. Herein, a tandem catalytic graphitization and nitrogen modification strategy for the synthesis of metal-free nitrogen-doped carbon nanoflakes (NCF) featuring the edge-suffused and graphite-analogous structure is presented. NCF exhibits superb Pt-like ORR activity (0.85 V for half-wave potential and 5.9 mA cm −2 for diffusion-limited current density) but much stronger robustness in the alkaline medium. The experimental and theoretical studies suggest the key role of graphitic-N in ORR. Furthermore, it unveils that the high activity of NCF should be traced to a synergistic polarization of the edge-type pyridinic-N/graphitic-N dipole spaced by one edge peak carbon atom on the armchair edges. This study sheds light on the understanding of ORR active sites in the nitrogen-doped nanocarbons for ORR.

Edge‐Rich Graphene Nanospheres with Ultra‐High Nitrogen Loading Metal‐Free Electrocatalysts for Boosted Oxygen Reduction

“…In general, the optimal graphitization degree and thus the conductivity of NGNs-900 has been achieved by manipulating the intensity and distribution of lattice defects in GNs through annealing. Comparisons of E onset , E 1/2 , and Tafel slop among NGNs-900 and previously reported ORR electrocatalysts are shown in Figure 5i, [16,[47][48][49][50][51][52][53][54] demonstrating NGNs-900 a topranked alkaline ORR electrocatalysts (Table S5). It is reasonable to conclude that the enhanced ORR performance of NGNs-900 might be attributed to its high N content (7.84 at%) and ultrahigh proportion of graphitic-N and pyridinic-N.…”

Constructing Structurally Ordered High‐Entropy Alloy Nanoparticles on Nitrogen‐Rich Mesoporous Carbon Nanosheets for High‐Performance Oxygen Reduction

“…[ 50 ] Second, the abundant N‐doping in the carbon framework increases the electron delocalization due to the good electron‐donating property of the N atom, forming abundant active sites for ORR. [ 51 ] Finally, the well‐dispersed structurally ordered HEA NPs not only provide more favorable surface for reactions but also prevent the loss of activity during the reaction applications, which may explain the excellent stability. The STEM elemental mapping of recycled OHEA‐mNC catalysts still shows the homogeneous distributions of Fe, Co, Ni, Cu, and Pd elements (Figure S21, Supporting Information), suggesting that the HEA structure is well retained.…”

Material design and surface chemistry for advanced rechargeable zinc–air batteries

“…[50][51][52][53][54][55][56] Metal-free carbon-based electrocatalysts showed superior ORR performances in both acidic and alkaline electrolytes. [57][58][59] In addition, it has emerged as a promising electrocatalyst owing to its advantages such as earth abundance, low price, environmental friendliness, and ease in tunability of their catalytic properties and structures. 60,61 Heteroatom doping strategies have been widely studied as an efficient way to improve the catalytic properties of metal-free carbon-based electrocatalysts.…”