Operando XANES from first-principles and its application to iridium oxide

Area of Science:

• Materials Science
• Electrochemistry
• Computational Chemistry

Background:

• Efficient electro-catalytic water splitting is crucial for sustainable energy technologies.
• Iridium oxide (IrO2) is an active but scarce catalyst for the oxygen evolution reaction (OER).
• Understanding the OER mechanism on IrO2 requires atomistic insights into its working environment.

Purpose of the Study:

• To investigate the electrochemical stability of IrO2 interfaces.
• To predict X-ray absorption near-edge structure (XANES) cross-sections under realistic conditions.
• To elucidate the OER mechanism on IrO2 at an atomistic level.

Main Methods:

• First-principles simulations combined with continuum solvent/electrolyte models.
• Operando X-ray absorption near-edge structure (XANES) experiments.
• Analysis of O K-edge and Ir L3-edge XANES spectra.

Main Results:

• Computed O K-edge XANES spectra support the formation of electron-deficient surface oxygen species.
• Surface hydroxyl groups are stable up to ~1 V and then oxidize.
• A shift in the Ir L3-edge cross-section agrees with experimental observations.

Conclusions:

• The study provides atomistic insights into the OER mechanism on IrO2.
• Simulations combined with experimental data enhance understanding of catalyst behavior.
• This work contributes to the rational design of novel OER catalysts.