Nanofabricated Catalyst Particles for the Investigation of Catalytic Carbon Oxidation by Oxygen Spillover

The catalytic oxidation of carbon by molecular oxygen was studied using C/Pt, Pt/C, Pt/Al₂O₃/C, Pt/CeO₂/C, Al₂O₃/C, and CeO₂/C model samples prepared by hole-mask colloidal lithography. By this technique, the degree of contact between platinum and carbon was controlled with high precision. The oxidation of carbon was monitored using atomic force microscopy and scanning electron microscopy. The results show that Pt in direct contact with carbon catalyzes the oxidation of carbon by spillover of dissociated oxygen from Pt to carbon. By physically separating Pt and carbon with a 10 nm thin spacer layer of Al₂O₃, the oxygen spillover was entirely blocked. However, through a corresponding spacer layer of CeO₂, carbon oxidation was still observed, either by oxygen spillover from Pt to carbon or directly dissociated on the ceria, although at a slower rate compared to the case with no spacer layer between Pt and carbon.