A General Descriptor for Single-Atom Catalysts with Axial Ligands

Area of Science:

• Materials Science
• Catalysis
• Computational Chemistry

Background:

• Single-atom catalysts (SACs) are crucial for various chemical reactions.
• Tuning SAC activity often involves decorating the active metal site with axial coordination ligands (ACLs).
• The precise mechanism by which ACLs regulate SAC performance remains incompletely understood.

Purpose of the Study:

• To investigate the regulatory mechanism of ACLs on SACs.
• To develop a general descriptor for quantifying the structure-activity relationship of ACL-SACs.
• To identify novel, highly active ACL-SACs for electrocatalytic applications.

Main Methods:

• Computational screening of diverse ACL-SAC combinations involving 3d-5d transition metals and ten prototype ACLs.
• Analysis of electronic structure changes, including M-O bonding energy levels and d-orbital dispersion.
• Development and application of a general structure descriptor (σ) and an axial ligand descriptor (σ_ACL).

Main Results:

• ACLs weaken metal atom adsorption by raising M-O bond energy levels and enhance d-orbital dispersion.
• A general structure descriptor (σ) was constructed, based on intrinsic features, to quantify ACL-SAC structure-activity relationships.
• The axial ligand descriptor (σ_ACL) shows potential for identifying rate-limiting steps in experimental settings.
• Predicted ACL-SACs (e.g., CrN₄-, FeN₄-, CoN₄-, RuN₄-, RhN₄-, OsN₄-, IrN₄-, and PtN₄-ACLs) exhibit superior activity for oxygen reduction and evolution reactions compared to benchmarks.

Conclusions:

• ACLs significantly influence SAC performance through electronic structure modulation.
• The developed descriptor σ provides a simple and cost-effective method for assessing efficient electrocatalysts.
• Identified ACL-SACs offer promising alternatives to current benchmark catalysts for oxygen electrocatalysis.