Discovery of Fe_2 =P-Type Ti(Zr/Hf)_2O_6 Photocatalysts toward Water Splitting

Abstract

We report the discovery of Fe_2P-type TiO_2-based photocatalysts, TiZr_2O_6 and TiHf_2O_6, through first-principle calculations. Appearing as the solid solutions of TiO_2 and Zr(Hf)O_2 at 150 GPa, Ti (Zr/Hf)_2O_6 unit cells are constructed by replacing two Ti atoms with Zr or Hf atoms in the pure Fe_2P-type TiO_2 lattice. The two compounds are mechanically and dynamically stable at ambient conditions. The electronic structure calculations predict direct bandgaps of 2.29 and 2.65 eV for TiZr_2O_6 and TiHf_2O_6, respectively. Significant evidence in the electronic properties prove both TiZr_2O_6 and TiHf_2O_6 to be attractive photocatalysts in the visible light region, but TiZr_2O_6 is more promising in the application of hydrogen generation by water splitting. Thus, instead of element doping, we narrow the bandgap of TiO_2 by developing intrinsic stable semiconductors from scratch. The rational design in this work of predicting high-pressure phases and stabilizing them open a way for prompting photoelectrochemical activities of photocatalysts.