Abstract
The photocatalytic reduction of carbon dioxide to renewable fuel or other valuable chemicals using solar energy is attracting the interest of researchers because of its great potential to offer a clean fuel alternative and solve global warming problems. Unfortunately, the efficiency of CO2 photocatalytic reduction remains not very high due to the fast recombination of photogenerated electron–hole and small light utilization. Consequently, tremendous efforts have been made to solve these problems, and one possible solution is the use of heterojunction photocatalysts. This review begins with the fundamental aspects of CO2 photocatalytic reduction and the fundamental principles of various heterojunction photocatalysts. In the following part, we discuss using TiO2 heterojunction photocatalysts with other semiconductors, such as C3N4, CeO2, CuO, CdS, MoS2, GaP, CaTiO3 and FeTiO3. Finally, a concise summary and presentation of perspectives in the field of heterojunction photocatalysts are provided. The review covers references in the years 2011–2021.
Highlights
Since the 18th century, together with the fast development of human society and the extensive use of fossil energy, environmental pollution has become increasingly serious with great environmental, social and economic impacts
When the g-C3N4 to AgTi mass ratio increased to 12%, this led to in an evident decrease in the photocatalytic reduction of CO2; this decreasing trend is ordinary, and it is possible to attribute it to the fact that an excessive amount of g-C3N4 resulted in shielding of the active site on the TiO2 surface
During the H2 evolution, the results showed that using Ar-purged gas, the TiO2/Cadmium sulfide (CdS) composite sample had better photocatalytic activity in comparison with the pristine TiO2
Summary
Since the 18th century, together with the fast development of human society and the extensive use of fossil energy, environmental pollution has become increasingly serious with great environmental, social and economic impacts. The conventional Z-scheme photocatalytic system is formed with two semiconductors (PS I and PS II) This type of heterojunction photocatalyst has the one limitation; they can solely be used in the liquid phase, in which they are not in physical contact, and an electron acceptor/donor (A/D) pair (Figure 4a), named the redox mediator. All prepared CeO2-TiO2 composites had higher photoactivity for the CO2 photoreduction to CH4 and CO, when compared with Mes-CeO2, Mes-TiO2 and commercial TiO2 photocatalyst (P25) This enhancement of the photocatalytic efficiency for these CeO2TiO2 photocatalysts was achieved due to the ordered large specific surface area, mesoporous architecture, 2D open-pore system that facilitates the diffusion of the reactant into the bulk of photocatalyst and provides fast intraparticle molecular transfer, and due to the absorption in the visible range due to the CeO2 species photosensitization. They concluded that loaded MoS2 nanosheets minimize the charge carrier recombination and enhance the conversion performance of the CO2 photoreduction into CH3OH due to the e− transfer from TiO2 to MoS2 [51]
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