Tuning of oxygen vacancy-induced electrical conductivity in Ti-doped hematite films and its impact on photoelectrochemical water splitting

• Published in: Scientific reports Vol. 10; no. 1; p. 7463
• Main Authors: Biswas, Pranab, Ainabayev, Ardak, Zhussupbekova, Ainur, Jose, Feljin, O'Connor, Robert, Kaisha, Aitkazy, Walls, Brian, Shvets, Igor V
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 04.05.2020; Nature Publishing Group UK
• Subjects: Annealing; Efficiency; Electrical conductivity; Ferric oxide; Iron; Oxygen; Pyrolysis; Splitting; Titanium; X-ray diffraction
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-020-64231-w

Titanium (Ti)-doped hematite (α-Fe O ) films were grown in oxygen-depleted condition by using the spray pyrolysis technique. The impact of post-deposition annealing in oxygen-rich condition on both the conductivity and water splitting efficiency was investigated. The X-ray diffraction pattern revealed that the films are of rhombohedral α-Fe O structure and dominantly directed along (012). The as-grown films were found to be highly conductive with electrons as the majority charge carriers (n-type), a carrier concentration of 1.09×10  cm , and a resistivity of 5.9×10 Ω-cm. The conductivity of the films were reduced upon post-deposition annealing. The origin of the conductivity was attributed firstly to Ti substituting Fe and secondly to the ionized oxygen vacancies (V ) in the crystal lattice of hematite. Upon annealing the samples in oxygen-rich condition, V slowly depleted and the conductivity reduced. The photocurrent of the as-grown samples was found to be 3.4 mA/cm at 1.23 V vs. RHE. The solar-to-hydrogen efficiency for the as-grown sample was calculated to be 4.18% at 1.23 V vs. RHE. The photocurrents were found to be significantly stable in aqueous environment. A linear relationship between conductivity and water-splitting efficiency was established.