Theoretical analysis of the modification of the redox potential in titania as a consequence of the nature and location of the dopant element

GABRIELA F. CABEZA; CECILIA I. N. MORGADE

Santa Fe

Conferencia; VI San Luis Conference; 2018

INCAPE-UNL

In the search ofnew catalytic materials, particularly in the design of materials based onsemiconductors such as titania, it is important not only to narrow the band gapto optimize the use of incident radiant energy but also modify the relativepositions of the valence and conduction bands, and with it theoxidation-reduction potentials for the catalysis of the desired reactions.It is known thatthe replacement of some atoms of the solid or the insertion of elements in thecrystal structure not only introduces localized levels whose energy fallswithin the gap but also modifies the relative positions of the valence andconduction bands with the consequent modification of the associated redoxpotentials. The n type dopingelements contributes with excess of electrons in the bulk providing localizedstates with energy close to the minimum of the conduction band. Analogously,acceptor impurities, p type dopinggenerate localized levels of energy close to the top of the valence band. In this work westudy from the analysis of the densities of states (DOS) how the insertion/substitutionof metallic elements such as V, Pt and Fe and non-metallic such as N, C and Fproduces not only the appearance of intra-gap acceptor states but alsodisplacements of the bands and the consequent modification of the redoxpotentials involved1-2. The adequate understanding of how doping elementsmodify the relative position of the bands and its consequent redox potentialvalue would allow the appropriate design of the catalyst according to thereaction to be catalyzed. The calculations were made using the VASP3code within the formalism of the Functional Density theory, with the inclusionof the Hubbard coefficient (DFT + U). The study was carried out on the bulk ofthe more stable polymorphs of titania, anatase and rutile. References 1.       Hui Yan,Xudong Wang, Man Yaon, Xiaojie Yao. ?Band structure design of semiconductors for enhancedphotocatalytic activity: The case of TiO2? Mat. Int., Vol. 23, No. 4, 402?407, 2013.2.       Morgade C. I.N., Cabeza, G. F. ?First-principles study of codoping TiO2systems capable of improving the specific surface area and the dissociation ofH2O to generate H2 and O2?, Comp. Mat. Scie., 127, 204?210, 2017.3.       KresseG., Furthmüller, ?Efficient iterative schemes for ab initio total energycalculations using a plane-wave basis set?, J.Phys. Rev. B 54, 11169, 1996.