The extensive exploitation of Degussa P25 (TiO2) for studies in photo-electrochemical splitting of water and photo-catalysis has to be rationalized even though, the objective of its use in reported studies is mainly for comparison purpose. Its remarkable reproducibility has to be recognized. It is presumed that P25 is a model core-shell system with anatase and rutile (4:1 weight ratio) and possibly the relative thickness of the core and shell of this system is most appropriate for its behaviour as a photocatalyst. It is necessary that one recognizes the relative values of surface energy of the polymorphs of TiO2in order to recognize the type of core shell configuration this system can adopt. The values of the surface energies of the three polymorphs of TiO2 are given in Table .