Pseudo-adsorption and long-range redox coupling during oxygen reduction reaction on single atom electrocatalyst

Area of Science:

• Electrocatalysis
• Materials Science
• Computational Chemistry

Background:

• Optimizing electrocatalysts requires understanding dynamic interfacial behaviors.
• The oxygen reduction reaction (ORR) is critical for energy conversion technologies.
• Single-atom catalysts offer high efficiency but their reaction mechanisms need detailed study.

Purpose of the Study:

• To investigate the ORR mechanism on transition metal single-atom sites embedded in N-doped nanocarbon.
• To elucidate the role of dynamic interfacial behaviors and solvation effects.
• To identify factors influencing electrocatalyst kinetics and efficiency.

Main Methods:

• Utilized ab initio molecular dynamics simulations with explicit solvation.
• Studied a series of transition metals (Fe, Co, Ni, Cu) on N-doped nanocarbon.
• Analyzed proton-coupled electron transfer (PCET) steps and intermediate species formation.

Main Results:

• Identified dissociative pathways and emerged solvated hydroxide species during PCET steps.
• Discovered that hydroxide species can exist in a dynamic 'pseudo-adsorption' state near the active site.
• Observed coupled dynamics between pseudo-adsorbed hydroxide and redox events within 1 ps.

Conclusions:

• Proton species can protonate pseudo-adsorbed hydroxide without direct catalyst surface contact, expanding the reactive region.
• This mechanism alleviates mass transfer limitations, significantly boosting reaction kinetics.
• Catalytic active regions may extend beyond direct surface binding, involving confined reaction species.