Phase-Dependent Photocatalytic Ability of TiO₂: A First-Principles Study

Abstract

The electronic properties of defected TiO2 were investigated using the first-principles calculations based on density functional theory and generalized gradient approximation. Three typical defects, oxygen vacancy, titanium interstitial, and titanium vacancy, were considered in three TiO2 polymorphs, anatase, rutile, and brookite, respectively. Our calculations demonstrated that the defect band is formed by removing an oxygen atom from or inserting an interstitial Ti atom into the TiO2 lattice, which is responsible for the improvement of photocatalytic ability due to the enhanced visible-light absorption. Our calculations further revealed that the defect formation energy increases as following brookite, anatase, and rutile, indicating that defects are easy to be created in brookite TiO2. The relatively high defect density and wide defect band contribute to the better photocatalytic performance of brookite TiO2 in visible light.

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).…”

“…The CO and CH 4 production from CO 2 photoreduction was in the order of brookite, anatase and rutile. Possible reasons for this superior activity of defective brookite include the facilitated formation of V O , faster reaction rate of CO 2 − with adsorbed H 2 O or surface OH groups, and an additional reaction route involving an HCOOH intermediate (Pan et al, 2009;Liu et al, 2012b). It is noted that V O , generated from thermal treatment with inert gas under the atmospheric pressure, was not stable in an air environment and was consumed during the photoreaction process (Liu et al, 2012a, b).…”

“…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 .…”

One‐Pot Synthesis of Cu‐Nanocluster‐Decorated Brookite TiO2Quasi‐Nanocubes for Enhanced Activity and Selectivity of CO2 Photoreduction to CH4

“…[15] Also, theoretical calculations indicatet hat brookite TiO 2 has larger band gap than anatase and rutile, which probably stems from the higher conduction band (CB) of brookite. [16] In 2012, high-qualityb rookite TiO 2 materials with various morphologies were fabricated, and the single-crystal nanosheets exhibited ab etter photodegradation activity for organic contaminants compared to other morphologies. [17] More recently,b rookite TiO 2 quasi-nanocubes (BTN) with high-phase purity were synthesized through ah ydrothermal methodi n our group.…”

Bandgap engineering of oxygen-rich TiO2+x for photocatalyst with enhanced visible-light photocatalytic ability

“…However, its efficiency is limited by its wide bandgap (*3.0 eV) because it could be activated only under the UV irradiation, and the photoinduced electron-hole pairs can recombine easily as well. To reduce the bandgap and improve the efficiency, considerable experimental and theoretical efforts have been carried out, such as doping (including metal, non-metal, and codoping) [2,[7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22], defect engineering (including oxygen vacancy and Ti interstitial) [23][24][25][26][27][28][29][30][31], and surface coating (such as metal and semiconductor nanoparticles) [32][33][34][35][36]. Recently, Etacheri et al [37] reported that the visible-light photocatalytic activity of undoped TiO 2 was achieved by increasing the amount of oxygen in TiO 2 .…”