Tuning Carbon Defect in Copper Single-Atom Catalysts for Efficient Oxygen Reduction.

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Defect chemistry in carbon materials is crucial for enhancing metal single-atom catalyst (SAC) performance.
• The oxygen reduction reaction (ORR) is vital for energy conversion technologies like fuel cells and metal-air batteries.

Purpose of the Study:

• To investigate the impact of tunable carbon defects on the ORR activity of copper single-atom catalysts (Cu-SACs).
• To develop a modified pyrolysis strategy for fabricating defect-engineered Cu-SACs.
• To understand the mechanism by which carbon defects enhance ORR performance.

Main Methods:

• Modified pyrolysis strategy to control carbon defect degree in Cu-SACs.
• Electrochemical characterization to evaluate ORR activity (half-wave potential, limiting current density, turnover frequency).
• Assembly and testing of Zn-air batteries using the optimized Cu-SACs.
• Density functional theory (DFT) calculations to elucidate the catalytic mechanism.

Main Results:

• Optimized Cu-SACs exhibited a high half-wave potential of 0.897 V_RHE and a limiting current density of 6.5 mA cm^-2.
• Superior turnover frequency of 2.23 e^- site^-1 s^-1 was achieved.
• Zn-air batteries demonstrated stable performance over 1100 hours of charge/discharge cycling.
• DFT calculations confirmed that carbon defects facilitate O-O bond weakening in the OOH* intermediate.

Conclusions:

• Tunable carbon defects in the carbon matrix significantly enhance the ORR activity of Cu-SACs.
• The developed modified pyrolysis strategy provides a universal approach for fabricating high-performance SACs.
• These defect-engineered Cu-SACs show great potential for advanced energy storage applications, particularly in Zn-air batteries.