Berlin 2015 – scientific programme

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O: Fachverband Oberflächenphysik

O 6: Catalysis

O 6.5: Talk

Monday, March 16, 2015, 11:45–12:00, MA 043

Surface oxide on Pt(111) as the active phase for NO and CO oxidation — •Matthijs A. van Spronsen, Joost W.M. Frenken, and Irene M.N. Groot — Huygens-Kamerlingh Onnes Laboratory, Leiden University, The Netherlands

Platinum finds its main application as a car catalyst to control the emission of exhaust gases. When the catalyst operates in excess oxygen, platinum catalyzes the oxidation of CO, NO, and remnant hydrocarbons. Despite platinum's wide use for catalytic oxidation, the active surface phase under oxygen-rich reaction conditions is still highly debated. Traditionally, it was believed that the bare metallic surface was the most reactive. But the recent development of new in situ surface science tools led to the discovery of phase transitions to states of higher activity for CO oxidation. The explaining models are ranging from a hyperactive oxygen-covered surface, surface oxide, or bulk oxide.

For the Pt(111) surface, the facet lowest in energy, it is also not clear what the relevant structure is under oxygen-rich reaction conditions. Both a surface oxide and a bulk α-PtO2 were found to be stable in different experiments. With the high-pressure, high-temperature ReactorSTM, we studied the oxidation of Pt(111) and found a stable surface oxide which assembles in a 'spoke wheel' superstructure at 1 bar O2 at 430 K. This surface oxide was also studied in both NO and CO oxidation under reaction conditions.