On the interpretation of XPS spectra of metal (Pt,Pt-Sn) nanoparticle/graphene systems

This Letter discusses the X-ray photoelectron spectroscopy (XPS) results of an article on Pt and Pt-Sn nanoparticles dispersed on graphene nanosheets. I argue that the authors' inter- pretation is largely unwarranted because it neglects the spin-orbit multiplicity and the branching ratio of XPS signals arising from electron levels with l > 0, and the fact that XPS peaks of given electron levels and given chemical species possess precise full with at half maximum (FWHM) values, and binding energy (BE) values. I suggest an interpreta- tion which offers a more accurate insight into the chemical composition and the catalytic properties of these nanoparticle systems.