Interfacial structures of Pt nanoparticles and transition-metal-oxide supports

Local structural properties at the interface of Pt nanoparticles (NPs) and transition-metal-oxide supports are examined using wavelet-transformed extended X-ray absorption fine structure (WT-EXAFS) with an enhanced resolution at Pt L-3 edge. The Pt NPs with a mean size of similar to 1 nm on TiO2 supports are synthesized using an incipient wetness method. EXAFS measurements are performed from the Pt NPs/TiO2 during heating from room temperature to 250 degrees C in an H-2 environment. Fourier-transformed EXAFS (FT-EXAFS) shows an absence of oxygen atoms around Pt atoms at T = 250 degrees C; meanwhile, the WT-EXAFS reveals a weak but distinguishable oxygen signal around Pt atoms. Pt-O bonds likely exist at the interface of Pt/TiO2 because oxygens on the outer surfaces of Pt NPs should be dissociated at T = 250 degrees C under an H-2 environment. This finding indicates that the combination of FT-EAXFS and WT-EXAFS can more accurately describe the heterogeneous interfaces of nanostructures.