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’ interpretation 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 interpretation which offers a more accurate insight into the chemical composition and the catalytic properties of these nanoparticle systems.