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 1 > 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. (C) 2013 Elsevier Ltd. All rights reserved.