The thousand and one faces of the titania

G. F. CABEZA

Santiago

Workshop; Workshop on Novel Methods for Electronic Structure Calculations; 2017

Departamento de Física, Facultad de Ciencias, Universidad de Chile

The titania (TiO2) is a semiconductor andhas its own name not only for its technological but also for its catalytic,including WGS reaction [1] and photocatalytic applications in its role as aphotocatalyst in remedial reactions of environmental contaminants [2-3]. It hasattracted interest in the study of possible modifications of it, in order tooptimize the absorption of solar radiation by changing its wide band gap (BG),its potential redox and the half-life of charge carriers generated in thetitania activation. Recently, experimental studies showed that monodopingwith anions or cations have not reached the expected efficiency but it has beenfound that the mixed doping with transition metals and nonmetals greatlyenhances the inhibition of recombination of charge carriers. Therefore, it isnecessary to know accurately which ones are the contributions that each dopingatom provides to the system. The accepted hypothesis is that the bandspartially occupied close to the VB, resulting from the presence of nonmetalimpurities, act as recombination centers (electrons of the partially occupiedimpurities states would annihilate the holes generated by the radiationabsorbed) or as mobility reduction centers of charge carriers (the states ofthe metal impurities, near the CB, would immobilize the excited electrons) [4].            On the other hand, gas sensors based on TiO2 films have beena subject of interest due to its high sensitivity and low cost. The sensingmechanism of this type of sensors is based on the conduction mechanism, whichis governed by the potential barriers formed at the inter-grains of thepolycrystalline structure. The shape of these potential barriers stronglydepends on the characteristics of the material, and then it is expected that adoping aggregation will affect significantly the conductivity and thus thesensitivity of the sensor.              Inthis talk a careful theoretical analysis of the energetic, structural andelectronic properties of doped and codoped titania [5, 6] and titania as metalsupport [7] will be presented with the aim to obtain insight into themetal-nonmetal effects as well as its applications in catalysis [8] and as agas sensor [9]. Some of the results presented have beencarried out in cooperation with experimental groups. [1] C. Vignatti, M. Avila, C.Apesteguía,  T. Garetto,  Inter. J. of Hyd. Energy 35 (2010) 7302.[2] S. Banerjee, J. Gopal,  P.Muralledharan, A. Tyagiand, B. Raj, Current Scie. 90 (2006) 1378.[3] L. Jinwen, R. Han, Y. Zhao, H. Wang, W. Liu, T. Yu, Y. Zhang, J. ofPhys. Chem. C 115 (2011) 4507.[4] D. Zhang, M. Yang, Phys. Chem.Chem. Phys 15 (2013) 18523.[5]C. I. N. Morgade, G. F.Cabeza, Comput. Mat. Scie. 127(2017) 204.[6] C. I. N.Morgade, G. F. Cabeza, Comput. Mat. Scie. 111 (2016) 513. [7] A. S.Maldonado, C. I. N. Morgade, S. B. Ramos, G. F. Cabeza, J. of Mol. Cat. A, 433C(2017) pp. 403.[8] C. I. N. Morgade,Ch. I. Vignatti, M. S. Avila, G. F. Cabeza, J. of Mol. Catal. A: Chemical 407 (2015) 102.[9] C. Buono, M. Desimone, F. Schipani, C. I. N. Morgade, Ch. I.Vignatti, G. F. Cabeza, C.    M. Aldao, J. of Electroceramics (2017), doi: 10.1007/s10832-017-0100-3.