Fig. 4.

Surface compositions and electronic properties. a XPS spectra of the 4 f level of Au. b XPS spectra of the 3d level of Pd. The Au and Pd binding energies were fitted by peak fitting techniques. Metallic Au, metallic Pd and Pd–O, which were the dominant contributors to each spectrum, were discussed. A distinct overlap could be observed between the Pd 3d_5/2 and the Au 4d_5/2 components for the bimetallic catalysts. The Au 4d_5/2 intensity was calculated from the well-resolved Au 4d_3/2 intensity, and this value was subtracted from the above overlapped peak to determine the Pd 3d_5/2 intensity. The resulting value was used to calculate the Au:Pd ratio