Asymmetrical FeN₄-O-FeO₄ Dual-Atom Sites in Fe─N─C for Robust pH-Universal Oxygen Reduction Reaction Catalysis

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• M-N-C single-atom catalysts show promise but are limited by symmetrical electronic density in M-N4 sites.
• Developing non-noble metal catalysts with enhanced intrinsic activity is crucial for energy applications.

Purpose of the Study:

• To design and synthesize an asymmetric Fe/Fe dual-center catalyst (FeN4-O-FeO4@NC) to overcome the limitations of symmetrical M-N4 moieties.
• To investigate the impact of asymmetric active sites on oxygen reduction reaction (ORR) performance and electron transfer efficiency.

Main Methods:

• Synthesis of a ZIF-8 derived Fe/Fe dual-center catalyst featuring adjacent Fe-N4 and O-FeO4 configurations.
• Characterization of the catalyst's electronic structure and active sites.
• Electrochemical evaluation of the catalyst's ORR activity in a pH-universal range and performance in liquid-state Zn-air batteries (ZABs).

Main Results:

• The FeN4-O-FeO4@NC catalyst exhibits asymmetric dumbbell-shaped active sites with an electron transfer pathway facilitating charge mobility.
• The asymmetric design breaks electronic symmetry, optimizes the d-band center, and enhances O2 activation.
• The catalyst demonstrates superior ORR performance across a pH-universal range and achieves a 1.502 V open circuit voltage and 246 mW cm-2 peak power density in ZABs, surpassing Pt/C.

Conclusions:

• The asymmetric FeN4-O-FeO4 dual-center catalyst significantly improves intrinsic activity for ORR.
• This work provides a new strategy for designing efficient, low-cost, and stable non-noble metal catalysts.
• The findings offer a paradigm for rationally designing advanced catalysts for energy conversion devices.