Ligand Engineering of Co-N₄ Single-Atom Catalysts for Highly-Active and Stable Acidic Oxygen Evolution

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Developing stable and efficient single-atom catalysts (SACs) for the oxygen evolution reaction (OER) in acidic media is crucial but challenging.
• Existing SACs often suffer from poor stability and activity in harsh acidic environments.

Purpose of the Study:

• To synthesize novel Co-N4 single-atom catalysts with controlled nitrogen coordination environments.
• To investigate the OER performance and stability of these SACs in acidic media.
• To elucidate the structure-activity relationships governing their catalytic behavior.

Main Methods:

• Ammonia-assisted pyrolysis for synthesizing Co-N4 SACs on crumpled graphene supports.
• Electrochemical characterization of OER activity and stability in 0.5 m H2SO4.
• Density functional theory (DFT) calculations and operando X-ray absorption spectroscopy (XAS) for mechanistic studies.

Main Results:

• Pyrrolic N4-coordinated Co sites exhibited superior OER activity (351 mV overpotential at 10 mA cm-2) compared to pyridinic counterparts.
• The pyrrolic coordination environment enhances OH- adsorption and OER kinetics.
• Exceptional long-term stability in acidic OER was achieved due to a multi-layered protective mechanism.

Conclusions:

• The pyrrolic N4 coordination is key to designing highly active and stable Co-based SACs for acidic OER.
• Controlled nitrogen coordination and support structure are critical for catalyst durability.
• This work offers fundamental insights for developing robust SACs for demanding electrochemical applications.