Phosphorus-Driven Electron Delocalization on Edge-Type FeN₄ Active Sites for Oxygen Reduction in Acid Medium

Abstract

Precise tuning of the chemical environment of neighboring atomic FeN 4 sites is extremely important for optimizing Fe−N−C catalysts to produce the fast oxygen reduction reaction (ORR) kinetics both in acidic and alkaline media, but it is actually very challenging. Heteroatoms could affect the metal charge of the active center through long-range electron delocalization; however, there are a few studies on it. Herein, density functional theory (DFT) calculations demonstrate that the addition of long-range P into edge-type FeN 4 can drive the electron delocalization and decrease the band gap of the FeN 4 center, leading to a substantial decrease in the free energy barrier to direct four-electron ORR kinetics compared to P-free edge-type FeN 4 , indicating superior intrinsic ORR activity. Experimentally, by incorporating P in edge-rich FeN 4 supported on N,P-doped carbon (Fe−N−C−P/N,P−C), the created Fe−N−C catalyst presents the greatly increased acidic ORR activity, with a half-wave potential (E 1/2 ) of 0.80 V (vs a reversible hydrogen electrode), which approaches that of commercial Pt/C and also has a high half-wave potential of 0.87 V, beyond Pt/C for alkaline ORR. In addition, it shows higher proton exchange membrane fuel cell and Zn-air battery performances than the pristine Fe−C−N catalyst (Fe−N−C/ N−C). This work will guide the rational design of highly active metal atomic scale catalysts with optimized chemical surroundings in terms of P incorporation as a chemically tunable method.

Metal‐Free Boron/Phosphorus Co‐Doped Nanoporous Carbon for Highly Efficient Benzyl Alcohol Oxidation

“…This is because the codoped heteroatoms are not on the same aromatic ring structure, which significantly increases the conjugation effect and electronic delocalization of the graphitic carbon. [ 33 , 34 ] The increased negative charge of the C atoms around B and the reduced positive charge of P in the graphitic carbon of BPC may enhance π – π interactions between BA and BPC to facilitate the dissociation of H during BA oxidation. This also contributes to the formation of a more stable transition state (ts) and an optimal reaction pathway.…”

Recent advances of biomass derived carbon-based materials for efficient electrochemical energy devices

“…Carbon materials have become an inevitable choice for electrode materials due to their abundant reserves, high electrical conductivity, and good cycle stability. 36 Different structural precursors endow carbon-based materials with different electrochemical behaviors. Various carbon materials have been extensively explored over the past decades, including crystalline nanocarbons and amorphous carbons (soft and hard carbons).…”

Doping Effect on Mesoporous Carbon-Supported Single-Site Bifunctional Catalyst for Zinc–Air Batteries

“…Most of the reported active center of Fe–N–C catalysts is one central Fe atom coordinated with four pyridine-N atoms (Fe–N 4 ) , whose local electron structure can be further modulated by additional heteroatoms. Recently, various multidoped Fe–N–C catalysts with Fe–N 5 , Fe–N 4 –O, Fe–N 3 S, , Fe–N 4 –S 2 , , Fe–N 4 –C–S, Fe–N 4 –P/S, Fe–N 3 P, and Fe–N x P y − atomic sites have been reported. It was proposed that the electron donation from the additional heteroatoms can break the symmetric electron density of the Fe atom in a Fe–N 4 unit to optimize the interactions with the intermediates and consequently further improve the ORR activities. − Though the influence of the additional heteroatoms on the central metal atoms has been intensively studied, their effect on the carbon matrix is less studied.…”