For both fresh and spent Ir-Mo/SiO2, analysis of their X-ray absorption near-edge structure (XANES) spectra at the Ir L3-edge confirm the metallic nature of Ir as analogously observed for the monometallic Ir/SiO2. However, the spectroscopic signature in Mo K-edge XANES is more complex: Mo already appears to be present in several oxidation states in the fresh Ir-Mo/SiO2 catalyst. Linear combination fit (LCF) analysis identifies Mo(VI), Mo(IV), and metallic Mo(0) as main components, with the respective reference spectra reproducing the observed spectrum (Figure and Figure ; see ESI for details). Note that due to the presence of several (at least 3) Mo (oxidation) states, Mo K-edge extended X-ray absorption fine structure (EXAFS) spectra of the fresh Ir-Mo/SiO2 catalyst cannot reliably be fitted.