Understanding the enhanced photoelectrochemical activity of Ta doped hematite

The improved photoactivity of Ta doped hematite, which was reported in our previous research, was studied by density functional theory (DFT) calculation and electrochemical measurement. The doping of Ta was calculated to produce slight changes in the local geometry of hematite crystal structure and have a low defect formation energy, indicating that the doping of Ta is energetically favorable and Ta impurity can be stably doped in hematite lattice to replace the Fe site (Ta-Fe). The analysis of the electronic structure of Ta doped hematite indicates that the transition level of corresponding Ta-FE(2+) defect (1.99 eV) lies below the conduction band minimum (CBM), meaning that the doping defect acts as shallow donor to provide more electron carrier, and thus improving the conductivity of hematite. The increased shallow donor density and the energy level induced by the doping of Ta were also confirmed by Mott-Schottky measurement. (C) 2017 Elsevier B.V. All rights reserved.