Facile Synthesis, Characterization, and Photocatalytic Activity of Hydrothermally Grown Cu2+-Doped ZnO–SnS Nanocomposites for MB Dye Degradation

Govinda Dharmana,Kisoo Yoo,Thirumala Rao Gurugubelli,Bathula Babu,Prabhakara Srinivasa Rao Masabattula

doi:10.3390/catal12030328

Abstract

The morphology, chemical composition, and doping process of metal oxides and sulfides play a significant role in their photocatalytic performance under solar light illumination. We synthesized Cu2+-doped ZnO–SnS nanocomposites at 220 °C for 10 h, using hydrothermal methods. These nanocomposites were structurally, morphologically, and optically characterized using various techniques, including powder X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV-visible absorption spectroscopy. Their photocatalytic activity (PCA) on methylene blue (MB) pollutant dye was examined under 150 W solar light illumination. Mixed-phase abundances with hexagonal ZnO and orthorhombic SnS structures were observed. TEM micrographs showed changes in morphology from spherical to nano-flake structures with an increasing doping concentration. XPS indicated the chemical states of the constituent elements in the nanocomposites. UV-visible absorption spectroscopy showed a decrease in the bandgap with an increasing doping concentration. Strong PCA was observed due to the separation of charge carriers, a change in bandgap, and a high light absorption ability under solar light irradiation. The measured photodegradation efficiency of the MB dye was approximately 97% after 2 h. The movement of the charge carriers and the bandgap alignment of the synthesized composites are briefly discussed.

Highlights

IntroductionOrganic dyes (pigments) and various types of herbicides (for example 2, 4-D, and 2,4-DCP) pollute freshwater bodies [1,2]
The ZnO–SnS nanocomposites were synthesized by a hydrothermal technique using the following steps: (1) 2.2 g (0.2 mol%) of Zn(CH3 COO)2 ·2H2 O in 50 mL of a deionized water-ethanol mixture (1:1 ratio) and equimolar NaOH in another deionized water-ethanol mixture were mixed drop by drop; (2) 50 mL of the deionized water-ethanol mixture of
Cu(NO3 )2 in 20 mL of the water-ethanol mixture was added to (1), which was stirred continuously for 3–4 h, before washing with deionized water and ethanol several times to extract impurities; (4) the resulting solution was poured into a Teflon-coated highvapor-pressure autoclave and placed in a high-temperature muffle furnace maintained at 220 ◦ C for 10 h; (5) the solution was centrifuged at 5000 rpm for 15 min

Summary

Introduction

Organic dyes (pigments) and various types of herbicides (for example 2, 4-D, and 2,4-DCP) pollute freshwater bodies [1,2]. These pigments reduce the quality of water in terms of pH and pose a high risk to people and aquatic life. The reduction of the toxicity levels of organic dyes such as methyl orange (MO), ciprofloxacin (CIP), methylene blue (MB), acid orange (AO), and rhodamine B (RhB) in freshwater bodies is crucial [3]. The current research priority is finding environmentally friendly and implementable methods for the removal of organic pollutants. Most organic dyes and other toxic industrial pollutants in water bodies can be removed using strategies [4] such as photocatalysis, reverse osmosis, and chemical and biological methods. Other advanced oxidation processes [5] such as ozonation and Fenton and non-thermal plasma processes degrade organic contaminants such as MB

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Results

Conclusion