A Density Functional Theory and Experimental Study of CO₂ Interaction with Brookite TiO₂

Abstract

The interactions of CO 2 with the (210) surface of brookite TiO 2 were studied using first-principle calculations on cluster and periodic slab 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 anatase TiO 2 (101) surface. Although the brookite (210) surface provided energetically similar CO 2 interactions as compared to the anatase (101) surface, the 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 reflectance Fourier transform infrared spectroscopy, confirms the presence of CO 2 − at significant levels on the oxygen-deficient brookite.

Understanding the Reaction Mechanism of Photocatalytic Reduction of CO2 with H2O on TiO2-Based Photocatalysts: A Review

“…Theoretical and experimental studies consistently showed that the CO 2 adsorption, activation, and dissociation processes were significantly influenced by the crystal phase of TiO 2 and the defect disorders in TiO 2 (Pan et al, 2009;He et al, 2010;Liu et al, 2012b;Rodriguez et al, 2012). Adsorption of CO 2 on the perfect and oxygen-deficient rutile (110), anatase (101) and brookite (210) surfaces has been investigated using dispersion-corrected density functional theory (DFT) and first-principles calculations (Markovits et al, 1996;Schobert et al, 2008;He et al, 2010;Rodriguez et al, 2012).…”

“…Adsorption of CO 2 on the perfect and oxygen-deficient rutile (110), anatase (101) and brookite (210) surfaces has been investigated using dispersion-corrected density functional theory (DFT) and first-principles calculations (Markovits et al, 1996;Schobert et al, 2008;He et al, 2010;Rodriguez et al, 2012). Compared with the defectfree surface, the presence of V O on the rutile (110), anatase (101) or brookite (210) surface induced the formation of new adsorption configurations, where CO 2 was bonded at the defect sites Indrakanti et al, 2011;Pipornpong et al, 2011;Sutter et al, 2011;Rodriguez et al, 2012). Although the interactions of CO 2 with the brookite (210) surface and anatase (101) surface have similar energy, the defect-free brookite surface had negligible charge transfer to the CO 2 molecule.…”

“…Although the interactions of CO 2 with the brookite (210) surface and anatase (101) surface have similar energy, the defect-free brookite surface had negligible charge transfer to the CO 2 molecule. Once defect disorders such as V O were created on the surface, the binding of CO 2 with brookite and anatase was favorable (Rodriguez et al, 2012). Electrons stored in the V O could be spontaneously transferred to CO 2 .…”

“…In addition to theoretical calculations (Markovits et al, 1996;Pan et al, 2009;He et al, 2010;Indrakanti et al, 2011;Pipornpong et al, 2011;Rodriguez et al, 2012), various microscopic (e.g., scanning tunneling microscopy (STM)) (Lee et al, 2011;Sutter et al, 2011) and spectroscopic (e.g., diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), electron paramagnetic resonance (EPR)) (Schilke et al, 1999;Ulagappan and Frei, 2000;Wu and Huang, 2010;Dimitrijevic et al, 2011;Yang et al, 2011;Liu et al, 2012a;Shkrob et al, 2012) studies have been conducted to understand the steps associated with CO 2 adsorption, activation, and dissociation. These steps are found to be significantly affected by crystal phases (e.g., anatase, rutile), surface acidic-basic sites (e.g., hydroxyl group), defect disorders (e.g., oxygen vacancy (V O )), co-adsorbates (e.g., H 2 O), and electronic structure (e.g., charge transport) of TiO 2 .…”

Brookite: Nothing New under the Sun?

“…Some insights in the factors determining the high intrinsic activity of brookite surfaces come from DFT calculations on the structure and adsorption properties of brookite (210) and anatase (101) surfaces, the most commonly exposed facets in nanocrystals [84,85]. The two surfaces are structurally similar, but the brookite (210) surface presents shorter interatomic distances and a different block arrangement.…”