Electronic properties of rutile and anatase TiO2 and their effect on CO2 adsorption: A comparison of first principle approaches

Abstract

• The choice of suitable functional is dependent on the desired property. • A high U value or hybrid functional is required for credible electronic properties. • Grimme D3 is needed for adsorptions, but not for electronic and optical properties. • Activated CO 2 displays strong adsorption, bending and charge transfer. Photocatalysis is a promising technique for utilizing solar light in chemical synthesis. Among several effective photocatalysts, TiO 2 remains the archetypal representative. Using density functional theory calculations, we characterized the geometric, mechanical, electronic and optical properties of rutile and anatase TiO 2 . We show that a proper choice of the functional and corrections is of paramount importance. While the geometric and mechanical properties are well reproduced with conventional GGA functionals, electronic properties require at least a Hubbard approach. Despite being revered as superior, hybrid functionals do not necessarily perform better and a prudent choice is required. On the contrary, a lower Hubbard correction is desirable for a proper description of interactions, defects and structures. Lastly, CO 2 adsorption was studied on several surfaces. Pristine anatase and rutile surfaces poorly activate CO 2 , with the exception of rutile (0 0 1), which binds CO 2 strongly in a bent form, showing considerable charge transfer and activation.