A Density Functional Theory Study of CO2 Interaction with Brookite TiO2 by

i ABSTRACT Over the past years, an interest has arisen in resolving two major issues: increased carbon dioxide (CO 2) emissions and depleting energy resources. A convenient solution would be a process that could simultaneously use CO 2 while producing energy. The photocatalytic reduction of CO 2 to fuels over the photocatalyst titanium dioxide (TiO 2) is such a process. However, this process is presently inefficient and unsuitable for industrial applications. A step toward making this process more effective is to alter TiO 2 based photocatalysts to improve their activity. The interactions of CO 2 with oxygen-deficient and unmodified (210) surfaces of brookite TiO 2 were studied using first-principle calculations on cluster systems. Charge and spin density analyses were implemented to determine if charge transfer to the CO 2 molecule occurred and whether this charge transfer was comparable to that seen with the oxygen-deficient and unmodified anatase TiO 2 (101) surfaces. Although the unmodified brookite (210) surface provided energetically similar CO 2 interactions as compared to the unmodified anatase (101) surface, the unmodified brookite surface had negligible charge transfer to the CO 2 molecule. This result suggests that unmodified brookite is not a suitable catalyst for the reduction of CO 2. However, the results also suggest that modification of the brookite surface through the creation of oxygen vacancies may lead to enhancements in CO 2 reduction. The computational results were supported with laboratory data for CO 2 interaction with perfect brookite and oxygen-deficient brookite. The laboratory data, generated using diffuse ii reflectance Fourier transform infrared spectroscopy, confirms the presence of CO 2-on only the oxygen-deficient brookite. Additional computational work was performed on I-doped anatase (101) and I-doped brookite (210) surface clusters. Adsorption energies and charge and spin density analyses were performed and the results compared. While charge and spin density analyses showed minute charge transfer to CO 2 , the calculated adsorption energies demonstrated an increased affinity for CO 2 adsorption onto the I-doped brookite surface. Gathering the results from all calculations, the computational work on oxygen-deficient, I-doped, and unmodified anatase and brookite surface structures suggest that brookite TiO 2 is a potential photocatalysts for CO 2 photoreduction.