Regulating Local Coordination Sphere of Ir Single Atoms at the Atomic Interface for Efficient Oxygen Evolution...

Area of Science:

• Catalysis
• Materials Science
• Electrochemistry

Background:

• Single-atom catalysts (SACs) are vital for efficient oxygen evolution reaction (OER) catalysis.
• Durability issues of SACs under harsh OER conditions limit their practical application.
• Weak metal-support interactions and metal dissolution compromise SAC performance.

Purpose of the Study:

• To enhance the performance and durability of single-atom catalysts for the oxygen evolution reaction (OER).
• To systematically regulate the local coordination of iridium single-atoms (Ir SACs) on a nickel oxide (NiO) surface.
• To investigate the impact of tailored atomic coordination on OER activity and stability.

Main Methods:

• Atomic-level modulation of Ir SACs' steric localization on NiO surface.
• X-ray absorption spectroscopy (XAS) to analyze metal-support interactions.
• Operando X-ray absorption and Raman spectroscopies for in-situ characterization.
• pH-dependence activity tests to evaluate catalytic performance.

Main Results:

• Embedded Ir single-atoms (Ir_emb-NiO) showed a 2-fold increase in Ir-Ni second-shell interaction, indicating stronger metal-support bonds.
• Ir_emb-NiO exhibited superior alkaline OER mass activity and long-term durability (1 mV/h degradation) compared to commercial IrO₂ and conventional Ir SACs.
• Operando studies revealed high-valence atomic Ir sites on NiOOH, utilizing a lattice oxygen mechanism and circumventing traditional scaling relationships.
• Enhanced Ir-Ni interaction imparted structural rigidity, mitigating Ir dissolution and ensuring sustained OER kinetics.

Conclusions:

• Tailoring the coordination sphere of Ir SACs by embedding them into NiO significantly enhances OER performance and durability.
• Stronger metal-support interactions are key to preventing metal dissolution and maintaining catalyst stability.
• The embedded Ir SACs operate via a lattice oxygen mechanism, offering a new pathway beyond conventional OER catalysis limitations.