It is well known that the loading of a noble metal (e.g. Pt, Pd) on an easily reducible Transition metal oxide (e.g. Co_3O_4, -Fe2_O_3, TiO_2 or MnO_2) results in an enhancement in the catalytic activity in CO oxidation at low temperatures due to interactions at the metal-support interface. However, the underlying nature of the interactions ("electronical" or "geometrical") is still under debate. Enhancing the CO oxidation activity in the low temperature range is of special interest for controlling automotive emissions during the cold start of a car (T< 250 C), where the strong CO adsorption on the noble metal remained an unsolved issue. The aim of the thesis was the synthesis of two different supported Pd catalysts, namely PdO/Co_3O_4 and PdO/-Fe_2O_3, their characterization in terms of structure and composition and the investigation of the influence of the Pd loading on the catalytic activity in CO oxidation. Furthermore, in situ studies were utilized to investigate dynamical interactions between the reactants and products and the catalyst surface under reaction conditions. The structural characterization of the catalysts was performed by transmission electron microscopy (TEM). As in situ methods, the Fourier Transform Infrared (FTIR) and the ambient-pressure X-ray photoelectron spectroscopy (APXPS) were applied. The catalysts were prepared by wet impregnation method yielding highly dispersed Pd particles with a mean size of sub-nm to 2 nm on the Co_3O_4 and of 5 to 10 nm on the -Fe_2O_3 support according to TEM images. The kinetic CO oxidation studies revealed that after Pd loading an enhancement of the activity was achieved for both catalysts. Interestingly, significant differences in the adsorption behavior of CO under reaction conditions could be observed. The in situ FTIR studies showed that on the PdO/Co_3O_4, no CO-Pd^o absorption bands were evident and only surface carbonate formation was detected, while on the PdO/Fe_2O_3 catalyst strong CO-Pd^o bands appeared already at RT indicating a reduction of PdO to metallic Pd by the CO. The CO-Pd^o bands on PdO/Fe_2O_3 were also present at higher temperatures (150 C), where a full CO conversion was observed. Thus, it was concluded that on both catalysts the CO oxidation rate was not affected by the well-known CO poisoning of Pd. In situ APXPS measurements confirmed the absence of metallic Pd on Co_3O_4 and the presence of stable PdO and PdO_2 phases under reaction conditions. Overall, the nature of CO adsorption sites and thus the CO oxidation pathways are apparently very different on the two catalysts. On PdO/Co_3O_4 the CO oxidation proceeds most likely via surface carbonates on the Co_3O_4 with PdO and PdO_2 acting as promoters, while on PdO/Fe_2O_3 metallic Pd provides adsorption sites for CO during the reaction.