Tip-like Fe-N₄ Sites Induced Surface Microenvironments Regulation Boosts the Oxygen Reduction Reaction

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Slow kinetics in oxygen electroreduction reactions (ORR) hinder efficient energy conversion.
• Single-atom catalysts (SACs) with tailored structures are crucial for improving ORR.
• Defined local structures and favorable microenvironments are key for SAC performance.

Purpose of the Study:

• To investigate the impact of tip-like FeN4 sites (T-Fe SAC) on surface microenvironments and catalysis.
• To elucidate the mechanism behind enhanced ORR kinetics at these novel sites.
• To evaluate the catalytic activity and stability of the developed T-Fe SAC.

Main Methods:

• Fabrication of tip-like FeN4 sites on spherical carbon supports.
• Finite Element Method (FEM) simulations to analyze electric fields and water layers.
• In situ spectroelectrochemical studies and Density Functional Theory (DFT) calculations.

Main Results:

• Tip-like FeN4 sites create a strong local electric field and a denser interfacial water layer.
• A pathway transition was observed, promoting O-O bond dissociation via side-on adsorption.
• The T-Fe SAC nanoreactor achieved excellent ORR activity (0.91 V vs. RHE) and stability, outperforming FeN4 and Pt/C.

Conclusions:

• Tip-like FeN4 sites significantly enhance ORR kinetics by optimizing the local electronic and solvation environment.
• The facile release of OH* on the curved surface further accelerates the oxygen reduction reaction.
• This study provides deep insights into SAC catalytic mechanisms, promising for industrial applications.