Characterization of adsorption sites on IrO₂via temperature programmed O₂ desorption simulations

Area of Science:

• Surface Science
• Computational Chemistry
• Catalysis

Background:

• Oxygen adsorption and desorption on iridium oxide (IrO2) are critical for the oxygen evolution reaction (OER).
• Understanding the kinetics of these elementary steps requires accurate modeling of surface processes.
• Density functional theory (DFT) provides valuable data for surface energy calculations.

Purpose of the Study:

• To simulate temperature-programmed desorption (TPD) profiles of oxygen (O2) from IrO2(110) using DFT-derived desorption energies.
• To investigate the role of different adsorption sites and surface coverages on O2 desorption kinetics.
• To provide insights into the surface reactivity of IrO2 relevant to catalytic applications like OER.

Main Methods:

• Utilizing density functional theory (DFT) to calculate oxygen adsorption and desorption energies on IrO2(110).
• Developing and applying computational models to simulate temperature-programmed desorption (TPD) profiles.
• Comparing simulated TPD data with experimental results for various oxygen coverages.

Main Results:

• The most stable adsorption site for oxygen on pristine IrO2(110) was identified as IrCUS, even at high coverages.
• Simulations accurately reproduced experimental TPD data when incorporating multiple adsorption sites.
• A novel step-related adsorption site (IrCUS-step-0.5) was identified as essential for matching experimental TPD profiles.
• Observed TPD peaks are attributed to distinct adsorption sites, not solely lateral interactions.

Conclusions:

• Multiple adsorption sites, including those at surface steps, significantly influence oxygen desorption behavior on IrO2(110).
• Computational simulations integrating DFT data and multiple adsorption sites are effective for predicting experimental TPD outcomes.
• This study enhances the understanding of oxygen surface chemistry on IrO2, impacting catalysis research, particularly for OER.