Some Unitary, Binary, and Ternary Non-TiO2 Photocatalysts

Abstract

Among all kinds of green earth and renewable energy projects underway, semiconductor photocatalysis has received wide interest because it provides an easy way to directly utilize the energy of either natural sunlight or artificial indoor illumination. TiO 2 , the most widely used photocatalyst, due to its wide band gap, can only be activated under UV irradiation, and thus, the development of novel semiconductor photocatalysts makes a significant advancement in photocatalytic functional materials. One of the effective strategies to overcome this shortcoming is photosensitizing these wide band gap semiconductors with narrow band gap semiconductors which have proper energy levels. This method can not only improve the photocatalytic activity, due to increasing visiblelight-harvesting efficiency, but also can decrease the recombination of the charge carriers, because the formation of n-n or n-p heterojunctions between the combined semiconductors can induce internal electric fields between them. In this regard, this review presents some unitary, binary, and ternary non-TiO 2 photocatalysts used for the degradation for organic pollutants and for water splitting.

Antibiotics Contaminated Irrigation Water: An Overview on Its Impact on Edible Crops and Visible Light Active Titania as Potential Photocatalysts for Irrigation Water Treatment

“…Binary heterojunctions are composed of two different semiconductors with different band gap energy levels (Marchelek et al, 2016). Conventional binary heterojunctions include type (I), type (II), and type (III) (Low et al, 2017).…”

“…Ternary heterojunctions are composed of three coupled semiconductors to form a ternary contact interface, which enhances electron excitation and photo-efficiency (Marchelek et al, 2016). Liu et al (Liu et al, 2021) used the hydrothermal method to construct a novel ternary composite heterojunction with superior photocatalytic properties, which consisted of a synthesized K-doped g-C 3 N 4 /TiO 2 /CdS (KCNNT@CdS) ternary heterojunction nanocomposite.…”

Semiconductor Nanocomposites for Visible Light Photocatalysis of Water Pollutants

“…•À the wide variety of organic pollutants in water are mineralized in to CO 2 and H 2 O [20]. The water splitting mechanism is given in Figure 4.…”

“…The problem is, the UV light makes only 4-5% of the solar spectrum while about 40-45% of the solar light falls in visible spectra. The need of UV light limits the photocatalytic activity due to its less availability [12,20].…”

“…A single pure semiconductor photocatalyst is unable to fulfill the all above mentioned requirements. Therefore, in order to enhance the photocatalytic activity of the SC, there is a need to enhance their visible light activity, which can either be done by enhancing the surface modifications, i.e., by increasing the surface area and porosity, or by chemicals modifications like doping of metals, non-metals, ions, non-metal co-doping, dye sensitization or by the formation of junctions unitary, binary and tertiary, i.e., semiconductor/semiconductor, semiconductor/metal, semiconductor/metal oxides or the semiconductors/nano-composites [20].…”