Mechanistic insights into metal, nitrogen doped carbon catalysts for oxygen reduction: progress in computational modeling

Abstract

Metal and nitrogen doped carbon materials (denoted as M-N-C) synthesized through high-temperature pyrolysis have been found to exhibit activity for oxygen reduction reaction (ORR) approaching that of Pt and electrochemical...

Spin-dependent active centers in Fe–N–C oxygen reduction catalysts revealed by constant-potential density functional theory

“…First-principles calculations have been employed to facilitate the assignment of the active FeN x C y centers for the ORR. 27 Various FeN x C y moieties have been proposed, including pyridinic FeN 4 C 10 , 28,29 pyrrolic FeN 4 C 12 , 30 FeN 4 C 10 with an axial ligand, 16,[31][32][33][34][35][36] and FeN 4 motif at the defected carbon matrix, 37 etc. Most theoretical studies focused on the local geometry and oxidation state of FeN x C y moieties; however, few theoretical studies have systematically explored the complete interplay of spin states, oxidation states, and applied potentials in determining the catalytic properties of Fe-N-C catalysts.…”

Precise Design and Modification Engineering of Single‐Atom Catalytic Materials for Oxygen Reduction

“…[92] Explicit water molecules are added around the reactants or above the surface to directly describe the interactions between reaction intermediates and solvent molecules in the explicit models. [93] Wang et al speculated ORR dynamics on a series of transition metal (M = Fe, Co, Ni, Cu) SACMs in nitrogen-doped nanocarbons by explicit solvation based on ab initio molecular dynamics (AIMD) reaction mechanism. [94] The dissociation pathways of all protoncoupled electron transfer (PCET) steps were determined at the electrochemical interface.…”

Unraveling the pH-Dependent Oxygen Reduction Performance on Single-Atom Catalysts: From Single- to Dual-Sabatier Optima

“…Metal–nitrogen-carbon (M–N–C) single-atom catalysts (SACs) have recently garnered significant attention. − They are highly promising due to their encouraging catalytic activity for the oxygen reduction reaction (ORR) and much lower costs compared with Pt-group metal (PGM) catalysts that are typically used to overcome the sluggish ORR kinetics in fuel cells and metal–air batteries. In recent years, there has been remarkable progress in the design, − synthesis, characterization, , catalytic activity, and stability evaluation ,, of M–N–C SACs.…”

“…Metal–nitrogen-carbon (M–N–C) single-atom catalysts (SACs) have recently garnered significant attention. − They are highly promising due to their encouraging catalytic activity for the oxygen reduction reaction (ORR) and much lower costs compared with Pt-group metal (PGM) catalysts that are typically used to overcome the sluggish ORR kinetics in fuel cells and metal–air batteries. In recent years, there has been remarkable progress in the design, − synthesis, characterization, , catalytic activity, and stability evaluation ,, of M–N–C SACs. Despite these advancements, the scientific community in this field has yet to reach a unified understanding of the pH dependence, the preference of the 4-/2-electron (4e – /2e – ) selectivity, and rate-determining steps of different M–N–C SACs, as highlighted in recent studies. − …”

“…Although conventional thermodynamic models can capture the trends for the 2e – and 4e – ORR, accurately predicting experimental observations, such as current density ( j ), half-wave potential ( E 1/2 ), and Tafel slope, remains difficult without microkinetic modeling. Moreover, modeling the pH-dependent activity and selectivity of M–N–C catalysts presents a tougher challenge due to the absence of pH/potential-dependent free energies . Recently, the origin of the high ORR activity of Fe-based M–N–C catalysts was considered to be the Fe-pyrrole-N species through DFT calculations .…”