A Dual-Atom La₂ Catalyst for the Oxygen Reduction Reaction.

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Rare earth elements, like lanthanum, possess unique electronic structures beneficial for catalysis.
• Single-atom lanthanum catalysts show limited activity in oxygen reduction reactions (ORR) due to electron deficiency.
• Developing efficient catalysts is crucial for advancing energy storage technologies like zinc-air batteries.

Purpose of the Study:

• To synthesize and characterize a novel dual-atom lanthanum catalyst on nitrogen-doped graphene (La₂-NG).
• To evaluate the catalytic performance of La₂-NG for the oxygen reduction reaction (ORR).
• To investigate the application of La₂-NG in zinc-air batteries and understand the underlying catalytic mechanisms.

Main Methods:

• Synthesis of La₂-NG catalyst using Joule ultrafast heating.
• Electrochemical evaluation of ORR activity, including half-wave potential measurements.
• Assembly and testing of La₂-NG based zinc-air batteries.
• Operando X-ray absorption spectroscopy (XAS) to study catalyst structural and electronic evolution.
• Theoretical calculations (e.g., DFT) to elucidate reaction mechanisms and energy barriers.

Main Results:

• The synthesized La₂-NG catalyst achieved a high half-wave potential of 0.893 V for the ORR.
• La₂-NG based zinc-air batteries exhibited an open circuit voltage of 1.52 V and a peak power density of 192 mW cm⁻².
• Operando XAS revealed dynamic changes in La valence states and the La₂-N₆ structure during ORR, indicating regulated intermediate adsorption/desorption.
• Theoretical calculations confirmed that the La₂-N₆ structure lowers the ORR energy barrier and enhances charge transfer.

Conclusions:

• Dual-atom lanthanum sites on N-doped graphene (La₂-NG) are highly effective ORR electrocatalysts.
• The unique La₂-N₆ moiety plays a critical role in facilitating the oxygen reduction reaction.
• La₂-NG demonstrates significant potential for high-performance zinc-air batteries.