ELECTRONIC PROPERTIES OF Ca AND Mg CoDoped ANATASE TiO2: A DFT STUDY

In the constant pursuit for green energy sources, there is a growing focus on materials that utilize solar energy efficiently in processes such as photocatalysis. TiO2 is one of the most widely studied semiconductor material that is suitable for photocatalytic applications. In particular, the anatase phase of TiO2 has been reported to demonstrate superior photocatatlytic performance compared to other naturally existing polymorphs, rutile and brookite. With a wide energy band gap however, of ≈ 3.2 eV, it is limited to be active in the UV region of the electromagnetic spectrum, which constitutes ≈ 4% of the solar energy spectrum. To improve its solar energy utilization efficiency, the effect of codoping alkaline earth metal acceptor dopant cations Mg2+ and Ca2+ within the TiO2 anatase lattice on the electronic properties has been investigated using the Density Functional Theory (DFT) method, using the state of the art Quantum ESPRESSO code. Dopant impurity states are introduced at the edge of the valence states which are lifted to higher energies and intersect the Fermi level upon alkaline earth metal codoping, an electronic structure modification that has been reported to improve the visible light responsiveness of the photocatalyst.