Structural imaging of surface oxidation and oxidation catalysis on Ru(0001)

Using simultaneous imaging and structural fingerprinting under reaction conditions, we probe the initial oxidation pathway and CO oxidation catalysis on Ru(0001). Oxidation beyond an initial (1×1)-O adlayer phase produces a heterogeneous surface, comprising a disordered trilayerlike surface oxide and an ordered RuO₂(110) thin-film oxide, which form independently and exhibit similar stability. The surface oxide and RuO₂ phases both show high intrinsic catalytic activity. The oxygen adlayer is inactive in isolation but becomes active due to cooperative effects in close proximity to the surface oxide.