Domain structure for an amorphous iridium-oxide water-oxidation catalyst characterized by X-ray pair distribution...

Area of Science:

• Materials Science
• Inorganic Chemistry
• Electrochemistry

Background:

• Amorphous iridium-oxide films are promising water-oxidation catalysts.
• Understanding their nanoscale structure is crucial for optimizing performance.
• The "blue layer" (BL) catalyst is electrodeposited from a soluble iridium precursor.

Purpose of the Study:

• To elucidate the domain structure of the amorphous blue layer iridium-oxide water-oxidation catalyst.
• To determine the fundamental building blocks and structural motifs within the BL film.
• To establish BL as a model system for studying catalyst assembly and mechanism.

Main Methods:

• X-ray pair distribution function (PDF) analysis was employed to characterize the film's atomic structure.
• The experimental PDF data was modeled using clusters derived from the rutile lattice.
• Structural distortions within the clusters were analyzed to understand deviations from ideal structures.

Main Results:

• The experimental PDF data was well-fitted by a single Ir5O22 cluster model.
• This cluster model incorporates distortions indicative of Ir(μ-O)3Ir or distorted Ir(μ-O)2Ir substructures.
• The BL catalyst exhibits remarkably small domain sizes and high homogeneity compared to other amorphous catalysts.

Conclusions:

• The Ir5O22 cluster represents the population-averaged distribution of metal-oxo clusters in the BL film.
• The observed distortions suggest deviations from a simple rutile structure.
• The BL catalyst's unique structural homogeneity and small domain size make it an excellent model for investigating catalyst assembly and water-oxidation mechanisms.