Tungsten Oxide: Defects, Dopants and Nanostructures.

Gianfranco Pacchioni

Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, Via R. Cozzi 53, 20125 Milano, Italy

We report the results of first principle DFT calculations based on a hybrid functional (CRYSTAL code) that properly reproduce band gap and other fundamental properties of WO3. We will briefly describe the dependence of the band gap on the crystalline phase of WO3 [1]. Then, we will address the nature of defects and dopants in bulk WO3. As WO3 can be easily reduced to WO3-x, we will discuss the nature of isolated O vacancies showing that three different situations arise from the removal of one O atom along each of the three crystallographic directions of monoclinic WO3 [2]. The data provide insight into the origin of electrochromism of this material. Then we will discuss the role doping of WO3 with substitutional atoms in order to increase the activity for water splitting [3,4] and we will show that Hf is a promising dopant. The redox properties of WO3 are discussed also in relation to H2 adsorption on the WO3(001) surface [5]. Finally, the role of nanostructuring will be analyzed by studying the properties of (WO3)3 cyclic clusters deposited on the rutile TiO2(110) surface [6,7]. Charge transfers at the (WO3)3/TiO2 interface and their role on the activity of this heterogeneous catalyst will be discussed.

[1] Wang F, Di Valentin C, Pacchioni G  J Phys Chem C 2011, 115, 8345

[2] Wang F, Di Valentin C, Pacchioni G Phys Rev B 2011, 84, 073103

[3] Wang F, Di Valentin C, Pacchioni G  ChemCatChem 2012, 4,476

[4] Wang F, Di Valentin C, Pacchioni G  J Phys Chem C 2012, 116, 8901

[5] Wang F, Di Valentin C, Pacchioni G  J Phys Chem C 2012, 116, 10672

[6] Di Valentin C, Rosa M, Pacchioni G  J Am Chem Soc 2012, 134, 14086

[7] Di Valentin C, Wang, F, Pacchioni G  Topics in Catal 2013 in press