Active Site Evolution of the TM-N₄-C Single-Atom Catalyst during the Oxygen Evolution Reaction

Area of Science:

• Electrochemistry
• Materials Science
• Computational Chemistry

Background:

• Single-atom catalysts (SACs) with transition-metal atoms in N-doped carbon (TM-N4-C) are promising for the oxygen evolution reaction (OER).
• The precise nature of active sites in SACs under working conditions remains poorly understood.

Purpose of the Study:

• Investigate the evolution of active sites for Fe, Co, and Ni SACs during the OER.
• Elucidate the relationship between metal d-band orbital location and active site composition.
• Provide insights into the stability of active sites under applied potentials.

Main Methods:

• First-principles calculations.
• Thermodynamic and kinetic simulations.

Main Results:

• Active site composition is strongly dependent on the metal d-band orbital location, decreasing in the order Fe > Co > Ni.
• Fe SACs are covered by *OH or *O; Co SACs are covered by *OH.
• Ni SACs feature a combined active site with *OH axial coordination and adjacent *O coverage.

Conclusions:

• The identified active site configurations are stable under applied electrode potentials.
• This work offers a detailed understanding of the OER pathway and active centers in TM-N4-C SACs.