Reinforcing CoO Covalency via Ce(4f)─O(2p)─Co(3d) Gradient Orbital Coupling for High-Efficiency Oxygen Evolution.

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Rare-earth (RE)-based transition metal oxides (TMO) are promising for the oxygen evolution reaction (OER).
• Understanding the electrocatalytic mechanisms and active sites in RE-TMO systems remains a significant challenge.

Purpose of the Study:

• To design and synthesize a model catalyst with atomically dispersed cerium on cobalt oxide (Ce SAs@CoO) using a plasma-assisted strategy.
• To investigate the origin of the enhanced OER performance in RE-TMO systems.
• To elucidate the electrocatalytic mechanism and identify active sites.

Main Methods:

• Plasma-assisted synthesis of atomically dispersed Ce on CoO (P-Ce SAs@CoO).
• Electrochemical testing for OER performance (overpotential, stability).
• X-ray absorption spectroscopy (XAS) and in situ electrochemical Raman spectroscopy.
• Theoretical calculations (density functional theory).

Main Results:

• The P-Ce SAs@CoO catalyst demonstrated superior OER performance with a low overpotential (261 mV at 10 mA cm⁻²) and enhanced stability compared to pristine CoO.
• Ce-induced electron redistribution was observed, which suppresses Co-O bond cleavage within the Co-O-Ce unit.
• Theoretical analysis revealed that gradient orbital coupling in the Ce(4f)-O(2p)-Co(3d) active site optimizes Co-3d-e_g occupancy, balancing intermediate adsorption for efficient OER.

Conclusions:

• The Ce-CoO model provides fundamental insights into the OER mechanism in RE-TMO catalysts.
• Atomically dispersed rare-earth elements can effectively tune the electronic structure and enhance catalytic activity.
• This work establishes a basis for designing high-performance RE-TMO catalysts for the oxygen evolution reaction.