Cobalt (II/III) oxide and tungsten (VI) oxide p-n heterojunction photocatalyst for photodegradation of diclofenac sodium under visible light

Malefane, Mope E.; Feleni, Usisipho; Kuvarega, Alex T.

doi:10.1016/j.jece.2019.103560

Cited by 79 publications

(15 citation statements)

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“…The reduction in electron and hole recombination of WO 3 can also occur with nanocomposites of cobalt(II, III) oxide and tungsten(VI) oxide. The synthesis of p-n heterojunction catalysts, such as Co 3 O 4 /WO 3 , was claimed to enhance the photoactivity under UV-or visible-light radiation [420]. The strong reduction in photoexcited electrons and holes resulted in the enhancement in diclofenac sodium degradation.…”

Section: Zno-womentioning

confidence: 99%

“…Higher generation of hydroxyl radicals (OH•) associated with the enhancement of effective charge separation was still advanced to explain the high photocatalytic activity of the CW2 sample. Figure 34 shows the charge transfer proposed by Malefane et al [420] and the p-n heterojunction formed to minimize photoexcited electron and hole recombination in CW2 nanocomposite. Among the post-transition metals, bismuth and gallium were evaluated in recently published works.…”

Section: Zno-womentioning

confidence: 99%

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Tungsten-Based Catalysts for Environmental Applications

2021

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This review aims to give a general overview of the recent use of tungsten-based catalysts for wide environmental applications, with first some useful background information about tungsten oxides. Tungsten oxide materials exhibit suitable behaviors for surface reactions and catalysis such as acidic properties (mainly Brønsted sites), redox and adsorption properties (due to the presence of oxygen vacancies) and a photostimulation response under visible light (2.6–2.8 eV bandgap). Depending on the operating condition of the catalytic process, each of these behaviors is tunable by controlling structure and morphology (e.g., nanoplates, nanosheets, nanorods, nanowires, nanomesh, microflowers, hollow nanospheres) and/or interactions with other compounds such as conductors (carbon), semiconductors or other oxides (e.g., TiO2) and precious metals. WOx particles can be also dispersed on high specific surface area supports. Based on these behaviors, WO3-based catalysts were developed for numerous environmental applications. This review is divided into five main parts: structure of tungsten-based catalysts, acidity of supported tungsten oxide catalysts, WO3 catalysts for DeNOx applications, total oxidation of volatile organic compounds in gas phase and gas sensors and pollutant remediation in liquid phase (photocatalysis).

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Section: Zno-womentioning

confidence: 99%

Section: Zno-womentioning

confidence: 99%

Tungsten-Based Catalysts for Environmental Applications

2021

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“…Type III system 22 The CB and VB of one semiconductor is between another Two systems are used and may possess different properties from the single components and increase light absorption range The exciton pair separation is not achieved; less stability of the system as redox reactions happen on one semiconductor p-n heterojunction 23 One semiconductor is a p-type and another one is an n-type Efficiently separate electrons and holes, improves photo- single photosystem. The developed heterostructures can be classified based on the direction and type of interaction and electron transfer as type I, type II, type III, and recently Zscheme heterojunctions.…”

Section: Uses Very Costly Noble Metalsmentioning

confidence: 99%

“…Formation of heterojunction photocatalysts is employed to improve the performance of individual semiconductor photocatalysts through a combination of two or more semiconductors in a single photosystem. The developed heterostructures can be classified based on the direction and type of interaction and electron transfer as type I, type II, type III, and recently Z-scheme heterojunctions. , The type I heterojunction is often referred to as the broken gap with a gap between the VB of one semiconductor (SC I) and the CB of the second semiconductor (SC II) without attainment of any possibility for electron and hole separation, which makes it unsuitable for photocatalytic applications (Figure c). The type III semiconductor heterostructure involves charge transfer from SC II to SC I such that all exciton pairs accumulate on the VB and CB of SC I due to its band edge positions being lower than that of SC II (Figure d).…”

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confidence: 99%

Understanding the Principles and Applications of Dual Z-Scheme Heterojunctions: How Far Can We Go?

Malefane

Mafa

Managa

et al. 2023

J. Phys. Chem. Lett.

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In the past seven years, dual Z-scheme heterojunctions evolved as favorable approaches for enhanced charge carrier separation through direct or indirect charge transfer transportation mechanisms. The dynamics of the charge transfer is the major strategy for understanding their photoactivity and stability through the formation of distinctive redox centers. The understanding of currently recognized principles for successful fabrication and classification in different energy and pollution remediation strategies is discussed, and a universal charge transfer-type-based classification of dual Z-schemes that can be adopted for Z-scheme and S-scheme heterojunctions is proposed. Methods used for determining the charge transfer as proof of dual Z-scheme existence are outlined. Most importantly, a new macroscopic N-scheme and a triple Z-scheme that can also be adopted as triple S-scheme heterostructures composed of four semiconductors are proposed for generating both oxidatively and reductively empowered systems. The proposed systems are expected to possess properties that enable them to harvest solar light to drive important chemical reactions for different applications.

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“…Diverse tactics investigated for possible improvement of the general efficiency of semiconductors for removal of pharmaceuticals include metal doping [9] , non-metal doping [10] , multi-elemental doping with metals and/or non-metals [11] , use of supports [12] , and formation of heterojunctions [13] , [14] . The contribution of heterojunctions towards abatement of different classes of pharmaceuticals such as β- blockers, hormones, antibiotics, cholesterol-lowering drugs, oestrogens, anti-psychotics, non-steroidal anti-inflammatory drugs (NSAIDs) and analgesics has been studied recently [15] , [16] , [17] , [18] , [19] , [20] .…”

Section: Introductionmentioning

confidence: 99%