Recent Advances in TiO-Based Heterojunctions for Photocatalytic CO Reduction With Water Oxidation: A Review.

Photocatalytic conversion of CO into solar fuels has gained increasing attention due to its great potential for alleviating the energy and environmental crisis at the same time. The low-cost TiO with suitable band structure and high resistibility to light corrosion has proven to be very promising for photoreduction of CO using water as the source of electrons and protons. However, the narrow spectral response range (ultraviolet region only) as well as the rapid recombination of photo-induced electron-hole pairs within pristine TiO results in the low utilization of solar energy and limited photocatalytic efficiency. Besides, its low selectivity toward photoreduction products of CO should also be improved. Combination of TiO with other photoelectric active materials, such as metal oxide/sulfide semiconductors, metal nanoparticles and carbon-based nanostructures, for the construction of well-defined heterostructures can enhance the quantum efficiency significantly by promoting visible light adsorption, facilitating charge transfer and suppressing the recombination of charge carriers, resulting in the enhanced photocatalytic performance of the composite photocatalytic system. In addition, the adsorption and activation of CO on these heterojunctions are also promoted, therefore enhancing the turnover frequency (TOF) of CO molecules, so as to the improved selectivity of photoreduction products. This review focus on the recent advances of photocatalytic CO reduction via TiO-based heterojunctions with water oxidation. The rational design, fabrication, photocatalytic performance and CO photoreduction mechanisms of typical TiO-based heterojunctions, including semiconductor-semiconductor (S-S), semiconductor-metal (S-M), semiconductor-carbon group (S-C) and multicomponent heterojunction are reviewed and discussed. Moreover, the TiO-based phase heterojunction and facet heterojunction are also summarized and analyzed. In the end, the current challenges and future prospects of the TiO-based heterostructures for photoreduction of CO with high efficiency, even for practical application are discussed.