Interaction between Ionic Liquids and a Pt(111) Surface Probed by Coadsorbed CO as a Test Molecule

Area of Science:

• Surface Science
• Physical Chemistry
• Materials Science

Background:

• Ionic liquids (ILs) are versatile materials with tunable properties.
• Understanding IL interactions with metal surfaces is crucial for catalysis and materials design.
• Carbon monoxide (CO) adsorption on platinum is a fundamental surface chemistry process.

Purpose of the Study:

• To investigate the effect of coadsorbed ionic liquids on CO desorption from a Pt(111) surface.
• To correlate the CO desorption temperature with the type of ionic liquid used.
• To establish a method for characterizing IL-metal surface interactions.

Main Methods:

• Temperature-programmed infrared reflection absorption spectroscopy (TP-IRAS) was employed.
• CO was coadsorbed with four different ionic liquids on a Pt(111) surface.
• Desorption temperatures of CO were measured and compared.

Main Results:

• CO desorbed at lower temperatures when ILs were present compared to a clean Pt(111) surface.
• The CO desorption temperature varied significantly depending on the specific ionic liquid.
• A clear order of CO desorption temperatures was observed: [C4C1Pyr][PF6] > [C4C1Pyr][NTf2] > [C2C1Im][NTf2] > [C4C1Pyr][OTf].

Conclusions:

• The interaction strength between the ionic liquid and the Pt(111) surface dictates CO desorption temperature.
• Stronger IL-Pt(111) interactions result in lower CO desorption temperatures.
• TP-IRAS of CO/IL coadsorbed systems is a viable method to characterize IL-metal surface interactions.