Green β-cyclodextrin exfoliated molybdenum sulphide based multifunctional poly(vinylidene fluoride) nanogenerators toward piezocatalytic water remediation

Abstract

Developing multifunctional materials that support both energy harvesting and environmental remediation is vital for the advancement of sustainable technologies. In this study, we present a green, scalable approach for exfoliating molybdenum disulfide (MoS₂) using β-cyclodextrin (β-CD) as an environmentally friendly intercalating and stabilizing agent. The resulting β-CD-exfoliated MoS₂ (MCD) nanofillers exhibited excellent dispersion, reduced layer thickness, and strong interfacial compatibility with the poly(vinylidene fluoride) (PVDF) matrix. Incorporation of MCD into PVDF (PMCD nanocomposites), prepared via melt-mixing and solution-casting, significantly promoted the nucleation of electroactive β- and γ-phases, as confirmed by FTIR, Raman spectroscopy, and WAXD, achieving a high polar phase content of ∼94%. To further elucidate the microstructural evolution, 2D Raman mapping was employed, which revealed the spatial distribution of α, β, and γ-phases within the PVDF spherulites in the nanocomposites. Raman analysis demonstrated that the nanofillers acted as heterogeneous nucleation centres, leading to oriented growth of electroactive PVDF chains and reduced spherulite size. The optimized PMCD (1 : 6) nanocomposite exhibited an enhanced piezoelectric coefficient (d₃₃ ∼ 88 pm V⁻¹) and dielectric constant (∼34 at 0.1 Hz). A flexible nanogenerator device fabricated from this film delivered an output voltage of ∼72 V under mechanical excitation. Furthermore, the device showed an excellent piezocatalytic degradation performance against Rhodamine B, Diclofenac, Ciprofloxacin, and Cr(VI), with degradation efficiencies reaching up to ∼69.2%, ∼71.4%, ∼62.5%, and ∼53.5%, respectively, under ultrasonic agitation. The enhanced catalytic activity was attributed to efficient charge separation and reactive species generation via the piezoelectric effect. This work offered a sustainable materials design strategy by combining green-exfoliated 2D nanofillers with an electroactive polymer, enabling the development of flexible nanogenerators and multifunctional environmental devices.