First principles study of hydrogen doping in anatase TiO₂

¹ Superconductivity Research Laboratory (SRL), Department of Physics, University of Tehran, North Kargar Ave., P.O. Box 14395-547, Tehran, Iran
² Department of Physics, Shahid Bahonar University of Kerman, P.O. Box 76169-133, Kerman, Iran

^a e-mail: zadeh@ut.ac.ir

Received: 30 December 2013
Revised: 15 June 2014
Accepted: 18 June 2014
Published online: 13 August 2014

Abstract

Hydrogen doping in the bulk of anatase TiO₂ was studied by density functional theory approach. Our results show that hydrogen atom prefers the interstitial sites which are closer to the oxygen atoms. Investigation of the electronic structures of different hydrogen doped systems indicates the increment of Fermi energy and bond length, affecting the instability of the system. Hydrogen doping in the anatase TiO₂ structure injects electron in the lower region of the conduction band, around the Ti states, leading Ti⁴⁺ toward Ti³⁺, while having no effect on the band gap energy value of TiO₂. Therefore, the observed hydrogen induced band gap narrowing in TiO₂ samples could be due to the structural disorders generated in the hydrogenation process. The hydrogen storage capacity of approximately 3 H atoms per supercell (Ti₃₂O₆₄) is also obtained, which is promising for renewable energy storage issue.