Ligand Modulation Induced Spin-State Transition Enhances Oxygen Electrocatalysis in Co Single-Atom Catalysts.

Area of Science:

• Catalysis
• Materials Science
• Physical Chemistry

Background:

• Understanding the interplay between ligand electronic structure, metal spin states, and catalytic activity is crucial for designing advanced single-atom catalysts (SACs).
• The precise relationship governing spin state regulation in magnetic SACs and its impact on bifunctional oxygen electrocatalysis remains an open area of research.

Purpose of the Study:

• To establish a fundamental link between ligand conjugation, cobalt (Co) spin state transitions, and catalytic performance in magnetic SACs.
• To develop a rational design principle for high-activity Co-based SACs for oxygen reduction and evolution reactions.

Main Methods:

• Employed grand-canonical density functional theory (DFT) and microkinetic simulations to investigate the electronic properties and reaction mechanisms.
• Correlated computational findings with experimental catalytic activity measurements.

Main Results:

• Demonstrated that increased ligand conjugation lowers the crystal field splitting energy of Co centers, favoring a transition from low-spin to high-spin configurations.
• Showcased how this spin state modulation alters intermediate binding, concurrently boosting both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activities.
• Identified a Co-based SAC with a high-spin Co site exhibiting excellent ORR (0.96 V vs. RHE) and OER (150 mV overpotential) performance in alkaline media.

Conclusions:

• Established a clear design principle linking ligand electronic structure to metal spin states for tuning SAC performance.
• The findings pave the way for the rational development of highly active magnetic SACs for bifunctional oxygen electrocatalysis.