Catalysis Letters, Vol.140, No.3-4, 147-150, 2010
Preparation and Characterization of Ce/N-Codoped TiO2 Particles for Production of H-2 by Photocatalytic Splitting Water under Visible Light by Sun et al. (Catal Lett (2010) 135:219)
I shall comment on the interpretation of XPS Ce3d spectra which Sun et al. propose in their paper. The area of major disagreement regards the authors' claim that these spectra provide evidence for the occurrence of both Ce3+ and Ce4+ ions at the surface of their catalysts and that the irradiation treatment affects the [Ce4+]/[Ce3+] atomic ratio.