Novel Z-Scheme/Type-II CdS@ZnO/g-C3N4 ternary nanocomposites for the durable photodegradation of organics: Kinetic and mechanistic insights

Elhussein M Hashem; Mahmoud A Hamza; Ayat N El-Shazly; Shaimaa A Abd El-Rahman; Esraa M El-Tanany; Rahma T Mohamed; Nageh K Allam

doi:10.1016/j.chemosphere.2020.128730

Novel Z-Scheme/Type-II CdS@ZnO/g-C₃N₄ ternary nanocomposites for the durable photodegradation of organics: Kinetic and mechanistic insights

Chemosphere. 2021 Aug:277:128730. doi: 10.1016/j.chemosphere.2020.128730. Epub 2020 Nov 3.

Authors

Elhussein M Hashem¹, Mahmoud A Hamza², Ayat N El-Shazly³, Shaimaa A Abd El-Rahman¹, Esraa M El-Tanany¹, Rahma T Mohamed¹, Nageh K Allam⁴

Affiliations

¹ Chemistry Department, Faculty of Science, Ain-Shams University, Abbassia, Cairo, Egypt.
² Chemistry Department, Faculty of Science, Ain-Shams University, Abbassia, Cairo, Egypt; Energy Materials Laboratory (EML), School of Sciences and Engineering, The American University in Cairo, New Cairo, 11835, Egypt.
³ Energy Materials Laboratory (EML), School of Sciences and Engineering, The American University in Cairo, New Cairo, 11835, Egypt; Central Metallurgical Research and Development Institute, P.O. Box 87, Helwan, Cairo, Egypt.
⁴ Energy Materials Laboratory (EML), School of Sciences and Engineering, The American University in Cairo, New Cairo, 11835, Egypt. Electronic address: nageh.allam@aucegypt.edu.

PMID: 33189399
DOI: 10.1016/j.chemosphere.2020.128730

Abstract

Visible-light-driven photocatalysis is a green and efficient strategy for wastewater treatment, where graphitic carbon nitride-based semiconductors showed excellent performance in this regard. Consequently, we report on the development of a green and facile one-pot room-temperature ultrasonic route for the preparation of novel ternary nanocomposite of cadmium sulfide quantum dots (CdS QDs), zinc oxide nanoparticles (ZnO NPs), and graphitic carbon nitride nanosheets (g-C₃N₄ NSs). The proposed materials had been characterized by several physicochemical techniques such as PXRD, XPS, FE-SEM, HR-TEM, PL, and DRS. The photocatalytic efficiency of the proposed photocatalysts was assessed towards the photodegradation of Rhodamine B dye as a water pollutant model using spectrophotometric measurements. The as-synthesized novel ternary nanocomposite (CdS@ZnO/g-C₃N₄) exhibited perfect photocatalytic activity, where almost complete degradation was achieved in only 2 h under UV-irradiation or 3 h under visible-irradiation. Various methods were used to elucidate the kinetics of the photocatalytic process. Moreover, CdS@ZnO/g-C₃N₄ exhibited a unique synergetic performance when compared to the corresponding binary composites or the individual components. This synergetic performance could be ascribed to the perfect electronic band configuration of the three components, leading to the establishment of several combined synergetic Z-Scheme/Type-II photocatalytic heterojunctions, which is the proposed mechanism for the observed synergetic photocatalytic reactivity of the as-synthesized CdS@ZnO/g-C₃N₄ nanocomposite when compared to the single and binary nanocomposite counterparts. Furthermore, the effects of both the type and concentration of various scavengers on the photocatalytic activity were assessed to investigate the most reactive species, where the reductive degradation pathway was found to be the predominant route. Finally, the photocatalytic efficiency of the as-synthesized CdS@ZnO/g-C₃N₄ composite showed promising and competing results when compared to other photocatalysts reported in the literature.

Keywords: CdS quantum Dots; Photocatalysts; Photocatalytic heterojunctions; Photodegradation; ZnO nanoparticles; g-C(3)N(4) nanocomposites.

MeSH terms

Catalysis
Kinetics
Nanocomposites*
Photolysis
Zinc Oxide*

Substances

Zinc Oxide