High-Resolution X-ray Photoelectron Spectroscopy of an IrO₂(110) Film on Ir(100)

Area of Science:

• Surface Science
• Materials Chemistry
• Computational Chemistry

Background:

• Iridium Dioxide (IrO2) is a critical material in catalysis and electrochemistry.
• Understanding the surface termination and species of IrO2 is essential for optimizing its performance.
• Previous characterization lacked detailed atomic-level insights into surface species and their formation.

Purpose of the Study:

• To characterize stoichiometric and hydroxyl-rich Iridium Dioxide (IrO2)(110) surfaces.
• To identify and assign core-level peaks corresponding to specific surface atoms and functional groups.
• To elucidate the formation mechanism of hydroxyl groups on the IrO2 surface.

Main Methods:

• High-resolution X-ray photoelectron spectroscopy (XPS) for surface elemental and chemical state analysis.
• Density functional theory (DFT) calculations for theoretical peak assignment and validation.
• Quantitative analysis of surface species concentrations and photoelectron kinetic energy dependence.

Main Results:

• Identified and assigned core-level Ir 4f and O 1s peaks for undercoordinated Ir/O atoms and bridging/on-top hydroxyl groups.
• Validated experimental peak assignments through DFT computations and quantitative surface analysis.
• Demonstrated that O2 exposure leads to significant on-top hydroxyl group formation via H2 reaction.

Conclusions:

• Established a reliable method for assigning XPS peaks on IrO2(110) surfaces.
• Provided atomic-level understanding of hydroxyl group formation on IrO2.
• The findings serve as a foundation for future XPS studies on IrO2 surface chemistry.