This paper reports alcohol decomposition on Pt nanoparticles. The catalytic degradation of 2-propanol into ethanol, methanol and finally water: 2-propanol → ethanol → methanol → water is observed during the photoreduction process of Pt^II leading to Pt nanoparticles. Formation of the intermediate products has been followed by UV-visible and IR spectroscopy. Quantum chemical results on the Pt₁₃ particle show that alcohol degradation is possible, and that the mechanism involves the deposition of H, C and CH fragments on the particle’s surface.