Enhanced reactive oxygen species mediated dye-degradation by H2O2 activation with different MoS2 nanostructures

Abstract

Organic dyes, extensively utilised in industry, pose significant environmental risks in wastewater. Exploring the catalytic potential of different forms of molybdenum disulfide (MoS₂) to address organic dye pollution is essential for environmental remediation. We demonstrate accelerated dye degradation assisted by an advanced oxidation process (AOP) in the dark, using progressively exfoliated forms of MoS₂ (bulk, nanoflakes, and nanosheets) in the presence of hydrogen peroxide (H₂O₂). MoS₂ nanosheets, exhibit ∼ 11 and 6 folds higher efficiency in the defect-mediated catalytic generation of hydroxyl (•OH) radical and singlet oxygen, respectively, than bulk, as revealed by terephthalic acid and 1,3 diphenylisobenzofuran assays, respectively. Direct electron paramagnetic resonance spectroscopy confirms at least 37 % higher generation of •OH radicals in the MoS₂ nanosheets than in the bulk. The AOP-assisted chemical degradation efficiency of methylene blue (MB) is ∼ 28, ∼ 73, and ∼ 89 % for MoS₂ bulk, nanoflakes, and nanosheets, respectively, over 1 hr. MoS₂ nanosheets can also chemically degrade other organic dyes, such as celestine blue (∼80 %) and malachite green (∼48 %). The dye-degradation mechanism is elucidated via the pseudo-first-order kinetic curve of catalytic activity of different MoS₂ forms with reaction constants of 0.00578, 0.02603, and 0.03463 min⁻¹ for bulk, nanoflakes, and nanosheets, respectively.