A universal N₂O₄-cavity strategy for precisely spaced, durable dual-atom ORR catalysts

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Diatomic catalysts show greater promise than single-atom catalysts for the oxygen reduction reaction (ORR).
• Controlling atomic spacing, maximizing performance, and suppressing degradation in conventional M-N4 frameworks remain challenging.

Purpose of the Study:

• To introduce an asymmetric N2O4 coordination strategy for diatomic catalysts.
• To synthesize and evaluate a MnMn-ON/C diatomic catalyst for ORR.
• To investigate the mechanisms behind the catalyst's performance and stability.

Main Methods:

• Synthesis of MnMn-ON/C diatomic catalyst using an oxygen-coordinated polydentate ligand-electrospinning strategy.
• Electrochemical characterization including half-wave potential (E1/2) measurements and long-term cycling stability tests.
• In situ spectroscopy and Density Functional Theory (DFT) calculations to elucidate reaction mechanisms.

Main Results:

• The MnMn-ON/C catalyst achieved a high E1/2 of 0.925 V, outperforming most reported asymmetric Mn-based diatomic catalysts.
• Exceptional stability was demonstrated, with only an 11 mV potential loss after 50,000 cycles and 1000 hours of stable operation in a zinc-air battery.
• DFT and spectroscopy revealed that N2O4 coordination enhances OOH adsorption and oxygen coordination tunes the electronic structure, while cavity confinement and Mn-O bonding prevent active site degradation.

Conclusions:

• The asymmetric coordination-cavity strategy provides precise control over diatomic spacing and mitigates performance degradation in non-precious metal ORR catalysts.
• This approach offers a general route for developing highly stable and efficient diatomic catalysts for energy applications.
• The strategy is extendable to other transition metals like Cobalt (Co), Copper (Cu), and Nickel (Ni).