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

Abstract

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 L3 edge. The Pt NPs with a mean size of ∼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 °C in an H2 environment. Fourier−transformed EXAFS (FT−EXAFS) shows an absence of oxygen atoms around Pt atoms at T = 250 °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 °C under an H2 environment. This finding indicates that the combination of FT−EAXFS and WT−EXAFS can more accurately describe the heterogeneous interfaces of nanostructures.