The Role of the Interface in CO Oxidation on Au/CeO2 Multilayer Nanotowers

The CO oxidation reaction is studied in this work using a controlled structure consisting of Au/CeO2 multilayers, in the form of towers of 10 x 10 mu m(2) base, with layer thicknesses in the nanometer range. This structure is prepared on a 3 '' Si wafer using reverse photolithography and vapor deposition in an e-beam chamber. The thickness of each layer is of nanometer dimensions and only the edges of the Au and CeO2 layers are exposed to the reaction gas mixture. The CO oxidation reaction rate is found to scale with the total length of the Au/CeO2 interfaces for nanotowers with the same total Au and CeO2 surface areas. TEM and X-ray diffraction (XRD) analyses reveal highly stressed gold films in the nanotowers, the lattice strain being temperature and film thickness dependent. Deactivation with time-on-stream is commensurate with relaxation of the gold films, as measured by a drop in their lattice strain.