High‐Performance Fe–N‐Doped Graphene Electrocatalysts with pH‐Dependent Active Sites for the Oxygen Reduction Reaction

Abstract

Advanced Fe–N‐doped graphene (FeNG) electrocatalysts are developed for the oxygen reduction reaction (ORR) by annealing a mixture of sustainable and low‐cost corn starch, urea, and FeCl3. The Fe–N coordinations and Fe/Fe3C nanoparticles can be controllably achieved through space confinement and pyrolysis temperature‐induced effects, respectively. Electrochemical tests show that, compared to the commercial Pt/C catalyst, the ORR half‐wave potential of FeNG is 99 mV more positive in KOH and 34 mV more negative in H2SO4, with higher stabilities in both media. More importantly, the ORR mechanisms of FeNG are demonstrated to be diverse in both KOH and H2SO4, owing to the various catalytic centers. The obtained results indicate that the enhanced ORR activity in basic media can mainly be ascribed to quaternary N and Fe/Fe3C sites, whereas the ORR performance in acidic media originates primarily from Fe–NX complexes. The electrocatalytic origin of these species is governed, primarily, by their unique electronic structures and specific environments in different pH solutions.

Platinum stabilized by defective activated carbon with excellent oxygen reduction performance in alkaline media

“…2), most likely due to that higher Pt loading amount is easy to facilitate the growth and aggregation of small Pt particles. The corresponding selected area electron diffraction (SAED) pattern in which further confirms the first-order reaction kinetics toward the dissolve of oxygen [39][40][41].…”

Theoretical Investigation on the Reaction Pathways of the Oxygen Reduction Reaction on Graphene Codoped with Manganese and Phosphorus as a Potential Nonprecious Metal Catalyst

“…The two linear Tafel regions are found with a slope of 40 mV dec −1 for the overpotential η <0.6 V and 120 mV dec −1 for η >0.6 V. A previous study indicated that on the Pt(1 1 1) surface, the Tafel slope is 54 mV dec −1 for η <0.38 V and 120 mV dec −1 for η >0.38 V . Thus, MnP 2 ‐Gra has a smaller Tafel slope at low overpotential region, which would lead to a fast ORR rate …”

“…The two linear Ta fel regionsa re found with as lope of 40 mV dec À1 for the overpotential h < 0.6 Va nd 120 mV dec À1 for h > 0.6 V. Ap reviouss tudy indicated that on the Pt(111) surface, the Ta fel slope is 54 mV dec À1 for h < 0.38 Va nd 120 mV dec À1 for h > 0.38 V. [43] Thus, MnP 2 -Gra has as maller Ta fel slope at low overpotential region, whichw ould lead to af ast ORR rate. [44] Conclusions Divacancy graphenes codoped with Mn and Pa re studied by using the density functional method. Our calculations show that MnP 2 -codoped divacancy graphene (MnP 2 -Gra) is energetically the most stable of the studied MnP x (x = 1-4) species.…”

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

“…Among the M-N x -C catalytic systems, Fe-N x -C electrocatalysts are studied most both experimentally [9][10][11][12]18,[24][25][26][27] and theoretically. 19,20,[28][29][30][31][32] In-depth structure-to-property relation presents an evidence that Fe-N x centers are the active sites playing a key role in oxygen reduction reaction.…”