Recent advances in constructing heterojunctions of binary semiconductor photocatalysts for visible light responsiveCO₂reduction to energy efficient fuels: A review

Abstract

Photocatalysis of carbon dioxide by the assistance of solar energy has been one of the most promising approaches to reduce CO 2 to renewable fuel. Several methods are pertained to enhance the photocatalytic activity for stimulating CO 2 reduction to selective fuels. Even though many researchers have been exploring methods of assembling a suitable semiconductor, practical constraints such as charge carrier recombination and low light utilization limit the photocatalytic activity. In this review, recent advancement in semiconductors and their characteristics toward the photoreduction of CO 2 has been comprehensively discussed. The major semiconductors that are discussed and analyzed based on their limitations in this review are TiO 2 , BiVO 4 , CdS, g-C 3 N 4 , ZnO, and MoS 2 -based composites. Initially, the fundamentals of heterogeneous photocatalysis such as the possible molecular pathways, product selectivity, and thermodynamics have been deliberated. Advancement in semiconductors in relation to quantum dots, heterojunction, and sacrificial reagent has been systematically analyzed. Doping and co-doping of semiconductors have proven to reduce the band gap notably and its outstanding electronic band position for the visible light photocatalysis has been identified. Furthermore, the developments of cocatalysts such as noble metals and nonmetals to stimulate photocatalysts performance in view of CO 2 reduction to value-added products have been disclosed. Specific developments in binary semiconductors through Z-scheme, S-scheme, and ternary heterojunction for charge separation and their characterization has been thoroughly deliberated. In addition, the role of doping, structural defects, as well as sensitization in enhancing the light harvesting abilities of the photocatalyst has been discoursed. The developments in photocatalytic reactors with their characteristics and limitations are also assiduously discussed. Finally, conclusions and future directions for photocatalysis of carbon dioxide toward renewable fuel production have been suggested.

A review of boron nitride-based photocatalysts for carbon dioxide reduction

“…The formaldehyde pathway finally results in CH 4 formation through simultaneous deoxygenation and hydrogenation (Fig. 3(c1)), while the carbene pathway eventually yields CH 4 and CH 3 OH as a result of deoxygenation and hydrogenation 31 (Fig. 3(c2)).…”

“…Regarding thermodynamics, the photocatalytic CRR does not proceed spontaneously since it is considered an uphill reaction, which is thermodynamically unfavourable and requires energy. 31 Moreover, CO 2 is a stable and nonpolar molecule with strong double covalent bonds (750 kJ mol −1 ) and therefore breaking these bonds to produce hydrocarbon fuels via the formation of C-H bonds (411 kJ mol −1 ) is associated with overcoming a large thermodynamic barrier through an uphill reaction. 32 These thermodynamic limitations signify that a suitable photocatalyst for CO 2 reduction needs to have two opposing aspects.…”

“…These factors are light harvesting, the band structure of semiconductor photocatalysts, charge carrier separation, surface active sites, activation and adsorption of reactants, and intermediate adsorption/desorption, which have been widely studied in the literature. 31,42,[48][49][50] Regarding reaction pathways in the CRR, the photocatalytic CRR is a complicated redox reaction process involving multiple electrons and protons, C]O bond cleavage, and C-H bond formation. 51 This, in turn, would result in the formation of several intermediate species and nal products in the pathway.…”

Titanium Carbide MXenes Cocatalyst with Graphitic Carbon Nitride for Photocatalytic H2 Production, CO2 Reduction, and Reforming Applications: A Review on Fundamentals and Recent Advances

“…Various semiconducting materials like titanium dioxide, zinc oxide, and other metal oxides are under exploration; however, they have lower photoactivity and are functional under UV-light irradiation. , Tremendous research has been conducted to find suitable materials with a broader range of visible light absorption, abundant active sites, and efficient charge carrier separation within the bulk structure and on the surface to carry out the photocatalytic reaction. , Among the semiconductors, graphitic carbon nitride (g-C 3 N 4 ) is regarded as an ideal photocatalyst for hydrogen production and CO 2 reduction applications . g-C 3 N 4 has excellent thermal and chemical stability suitable for use in harsh reaction environments and can be synthesized from inexpensive and abundant raw materials, such as melamine and urea, making it a cost-effective alternative to other photocatalyst materials.…”

Visible-light-driven photocatalytic selective oxidation of amines and sulfides over a vanadium metal–organic framework

“…[4][5][6][7][8] However, the application potential of semiconductor materials is limited due to their inefficient visible-light utilization and poor selectivity for the desired products. 9 Therefore, the development of new photocatalysts with a high efficiency and selectivity is essential for the conversion of organic chemicals.…”