2a shows that both Pt/C and Pt–Ag/C samples exhibit the crystalline facecentered cubic (fcc) structure of platinum at 2θ (indicated by asterisks). However, the fcc structure corresponding to XRD diffraction patterns of silver was not detected. Results suggest that the sizes of Ag entities were amorphous or were smaller than the detection limit (1–2 nm) of the XRD technique [1,26,27]. A more sensitive