Discovery of CO2 precursor in the reaction of CO and O on Pt(111)

Using the technique of Cs+ reactive ion scattering (Cs+ RIS), we show that reaction of CO and O on a Pt(111) surface produces a CO2 precursor species that remains stable on the surface up to 300 K. The CO2 species desorbs with an activation energy of 46±3 kJ mol−1, whereas the direct CO2 gas formation via Langmuir–Hinshelwood (LH) reaction between CO and O occurs with an activation energy of 75±4 kJ mol−1. The observation reveals a new pathway for CO oxidation reaction, which is different from the direct LH pathway.