Lattice disorders of TiO2 and their significance in the photocatalytic conversion of CO2

Developing economic strategies for the conversion of carbon dioxide, given its potential impact on global climate change, has become necessary for the long-term sustainability of the planet Earth. From traditional thermochemical routes, CO2 conversion requires a substantial amount of costly energy, which in itself produces CO2. Utilizing solar energy, particularly radiation in the visible spectrum, can be the most efficient method for supplying the energy requirement. This review explores TiO2, and its various polymorphs, as a catalyst component in CO2 photoconversion. Titania is an abundant resource that would make for a low-cost catalytic material. As shown in this work, crystal lattice defects in TiO2 can be systematically tailored to yield a photocatalyst that provides optimum adsorption and activation of CO2 on the TiO2 surface and allows sufficient electron-hole separation times. These separation times are necessary for efficient surface site chemistries to occur. In addition to synthesis techniques, this review also describes the latest characterization tools used to investigate lattice defects, including oxygen vacancies, as well as corresponding Density Functional Theory (DFT) studies. Two key features of this work will be (1) defining the relationship between the lattice defects and (2) the Fermi Energies that are paramount for activating the catalyst in the visible region. The catalyst is thereby optimized by controlling these defects. Furthermore, TiO2-based hybrid photocatalysts and their corresponding lattice defects in photoconversion of CO2 to useful products are discussed.