Epitaxial TiO 2 Thin Film Photoanodes: Influence of Crystallographic Structure and Substrate Nature

H. Magnan (1, 2) , Dana Stanescu (1, 2) , M. Rioult (3) , E. Fonda (3) , A. Barbier (1, 2)

1 LNO - Laboratoire Nano-Magnétisme et Oxydes
2 SPEC - UMR3680 - Service de physique de l'état condensé
3 SSOLEIL - Synchrotron SOLEIL

Photocatalysis and photoelectrochemical (PEC) activities not only strongly depend on the chemical formulae of the electrode materials, but also on the local ionic environment that deserves to be addressed in detail for a given compound. Specifically, within the framework of PEC water splitting, we studied the growth, crystal and electronic structures, and the PEC properties of thin epitaxial films of TiO2 deposited on Pt(111), Pt(001), and Nb:SrTiO3(001) substrates. We found that the crystallographic structure is respectively rutile (100), anatase (001) on interfacial TiO2–B(001), and anatase (001). We studied in detail the relevant electronic properties such as band gap, position of valence and conduction bands, flat-band potential, and charge carrier density. We demonstrate that the largest photocurrent is obtained for rutile (100) deposited on Pt(111) owing to a higher position of the conduction band, whereas the lowest photocurrent is obtained for anatase (001) deposited on Nb:SrTiO3(001) due to a detrimental larger band gap. This study shows that for pure phase epitaxial layers, rutile (100) is much more efficient than anatase (001) for solar water splitting. Our results suggest that biphase heterojunctions may be a fruitful route to tune the properties allowing for PEC photoanode improvement.

Domaines: Science des matériaux [cond-mat.mtrl-sci]; Matériaux

H. Magnan, Dana Stanescu, M. Rioult, E. Fonda, A. Barbier. Epitaxial TiO 2 Thin Film Photoanodes: Influence of Crystallographic Structure and Substrate Nature. Journal of Physical Chemistry C, 2019, 123 (9), pp.5240-5248. ⟨10.1021/acs.jpcc.8b11479⟩. ⟨hal-02437093⟩