Desorption Kinetics of Carbon Dioxide from a Graphene-Covered Pt(111) Surface

The interaction of carbon dioxide (CO₂) with a graphene-covered Pt(111) surface was investigated using temperature-programmed desorption (TPD) and reflection absorption infrared spectroscopy (RAIRS). The TPD spectra show monolayer and multilayer desorption peaks; however, the multilayer peak is not well-separated from the monolayer peak. The TPD spectra for submonolayer and multilayer coverages align on separate common leading edges. This alignment is a signature of zero-order desorption kinetics. The RAIRS spectra for submonolayer coverages have a relatively sharp peak at ∼2350 cm^-1, which is assigned to the ν₃ asymmetric stretch. The peak is observed at the onset of CO₂ adsorption, and the area of the peak increases linearly with coverage. This suggests that CO₂ does not lie flat on the surface but instead has a component of its bond axis perpendicular to the graphene surface.