Platinum nanoparticles deposited either by the photodeposition method or by the carbonyl chemical route are thought to be electronically modified onto carbon support. The deposition method is responsible for a controlled heterogeneous nucleation of platinum nanoparticles onto the substrate. By coupling results obtained from CO stripping experiments and X-ray photoelectron spectroscopy (XPS), there was a strong interaction between graphitic domains of carbonaceous supports and platinum nanoparticles. This phenomenon is at the origin of an increase of CO tolerance of the catalyst.